Once upon a time around 2001 or so I used to have a static line at home and host some stuff on my home linux box. A windows NT update had meant a lot of them had enabled this optimistic encryption thing where windows boxes would try to connect to a certain port and negotiate an s/wan before doing TCP traffic. I was used to seeing this traffic a lot on my firewall so no big deal. However there was one machine in particular that was really obnoxious. It would try to connect every few seconds and would just not quit.
I tried to contact the admin of the box (yeah that’s what people used to do) and got nowhere. Eventually I sent a message saying “hey I see your machine trying to connect every few seconds on port <whatever it is>. I’m just sending a heads up that we’re starting a new service on that port and I want to make sure it doesn’t cause you any problems.”
Of course I didn’t hear back. Then I set up a server on that port that basically read from /dev/urandom, set TCP_NODELAY and a few other flags and pushed out random gibberish as fast as possible. I figured the clients of this service might not want their strings of randomness to be null-terminated so I thoughtfully removed any nulls that might otherwise naturally occur. The misconfigured NT box connected, drank 5 seconds or so worth of randomness, then disappeared. Then 5 minutes later, reappeared, connected, took its buffer overflow medicine and disappeared again. And this pattern then continued for a few weeks until the box disappeared from the internet completely.
I like to imagine that some admin was just sitting there scratching his head wondering why his NT box kept rebooting.
The lesson for any programmers reading this is to always set an upper limit for how much data you accept from someone else. Every request should have both a timeout and a limit on the amounts of data it will consume.
I enjoyed reading this, thank you for sharing. When you say you tried to contact the admin of the box and that this was common back then, how would you typically find the contact info for an arbitrary client's admin?
You can also find out who owns a general group of IP addresses, and at the time they would often assist you in further pinpointing who is responsible for a particular address.
I had a ton of trouble opening a 10MB or so png a few weeks back. It was stitched together screenshots forming a map of some areas in a game, so it was quite large. Some stuff refused to open it at all as if the file was invalid, some would hang for minutes, some opened blurry. My first semi-success was Fossify Gallery on my phone from F-Droid. If I let it chug a bit, it'd show a blurry image, a while longer it'd focus. Then I'd try to zoom or pan and it'd blur for ages again. I guess it was aggressively lazy-loading. What worked in the end was GIMP. I had the thought that the image was probably made in an editor, so surely an editor could open it. The catch is that it took like 8GB of RAM, but then I could see clearly, zoom, and pan all I wanted. It made me wonder why there's not an image viewer that's just the viewer part of GIMP or something.
Among things that didn't work were qutebrowser, icecat, nsxiv, feh, imv, mpv. I did worry at first the file was corrupt, I was redownloading it, comparing hashes with a friend, etc. Makes for an interesting benchmark, I guess.
That's a 36,000x20,000 PNG, 720 megapixels. Many decoders explicitly limit the maximum image area they'll handle, under the reasonable assumption that it will exceed available RAM and take too long, and assume the file was crafted maliciously or by mistake.
Firefox on a mid-tier Samsung and a cheapo data connection (4G) took avout 30s to load. I could pan, but it limited me from zooming much, and the little I could zoom in looked quite blury.
On Firefox on Android on my pretty old phone, a blurry preview rendered in about 10 seconds, and it was fully rendered in 20 something seconds. Smooth panning and zooming the entire time
For what it's worth, this loaded (slowly) in Firefox on Windows for me (but zooming was blurry), and the default Photos viewer opened it no problem with smooth zooming and panning.
Safari on my MacBook Air opened it fine, though it took about four seconds. Zooming works fine as well. It does take ~3GB of memory according to Activity Monitor.
"On 21 September 1997, the USS Yorktown halted for almost three hours during training maneuvers off the coast of Cape Charles, Virginia due to a divide-by-zero error in a database application that propagated throughout the ship’s control systems."
" technician tried to digitally calibrate and reset the fuel valve by entering a 0 value for one of the valve’s component properties into the SMCS Remote Database Manager (RDM)"
Though, bots may not support modern compression standards. Then again, that may be a good way to block bots: every modern browser supports zstd, so just force that on non-whitelisted browser agents and you automatically confuse scrapers.
If you nest the gzip inside another gzip it gets even smaller since the blocks of compressed '0' data are themselves low entropy in the first generation gzip. Nested zst reduces the 10G file to 99 bytes.
Can you hand edit to create recursive file structures to make it infinite? I used to use debug in dos to make what appeared to be gigantic floppy discs by editing the fat
It would need a bot that is accessing files via hyperlink with an aim to decompress them and riffle through their contents. The compressed file can be delivered over a compressed response to achieve the two layers, cutting down significantly on the outbound traffic. passwd.zst, secrets.docx, etc. would look pretty juicy. Throw some bait in honeypot directories (exposed for file access) listed in robots.txt and see who takes it.
> At my old employer, a bot discovered a wordpress vulnerability and inserted a malicious script into our server
I know it's slightly off topic, but it's just so amusing (edit: reassuring) to know I'm not the only one who, after 1 hour of setting up Wordpress there's a PHP shell magically deployed on my server.
There's a lot of essential functionality missing from WordPress, meaning you have to install plugins. Depending on what you need to do.
But it's such a bad platform that there really isn't any reason for anybody to use WordPress for anything. No matter your use case, there will be a better alternative to WordPress.
Can you recommend an alternative for a non-technical organization, where there's someone who needs to be able to edit pages and upload documents on a regular basis, so they need as user-friendly an interface as possible for that? Especially when they don't have a budget for it, and you're helping them out as a favor? It's so easy to spin up Wordpress for them, but I'm not a fan either.
I've tried Drupal in the past for such situations, but it was too complicated for them. That was years ago, so maybe it's better now.
I find it very telling that there's no 2 responses to this post recommending the same thing. Confirms my belief that there is no real alternative to Wordpress for a free and open-source CMS that is straightforward to install and usable to build and edit pages by non-tech-experts.
> Can you recommend an alternative for a non-technical organization, where there's someone who needs to be able to edit pages and upload documents on a regular basis, so they need as user-friendly an interface as possible for that
25 years ago we used Microsoft Frontpage for that, with the web root mapped to a file share that the non-technical secretary could write to and edit it as if it were a word processor.
Somehow I feel we have regressed from that simplicity, with nothing but hand waving to make up for it. This method was declared "obsolete" and ... Wordpress kludges took its place as somehow "better". Someone prove me wrong.
Yes I can. There's an excellent and stable solution called SurrealCMS, made by an indie developer. You connect it by FTP to any traditional web design (HTML+CSS+JS), and the users get a WYSIWYG editor where the published output looks exactly as it looked when editing. It's dirt cheap at $9 per month.
Edit: I actually feel a bit sorry for the SurrealCMS developer. He has a fantastic product that should be an industry standard, but it's fairly unknown.
Jekyll and other static site generators do not repo Wordpress any more than notepad repos MSWord
In one, multiple users can login, edit WYSIWYG, preview, add images, etc, all from one UI. You can access it from any browser including smart phones and tablets.
In the other, you get to instruct users on git, how to deal with merge conflicts, code review (two people can't easily work on a post like they can in wordpress), previews require a manual build, you need a local checkout and local build installation to do the build. There no WYSIWYG, adding images is a manual process of copying a file, figuring out the URL, etc... No smartphone/tablet support. etc....
I switched by blog from wordpress install to a static site geneator because I got tired of having to keep it up to date but my posting dropped because of friction of posting went way up. I could no longer post from a phone. I couldn't easily add images. I had to build to preview. And had to submit via git commits and pushes. All of that meant what was easy became tedious.
what are your favorite static site generators? I googled it and cloudflare article came up with Jekyll,Gatsby,Hugo,Next.js, Eleventy. But would like to avoid doing research if can be helped on pros/cons of each.
I looked recently when thinking of starting some new shared blog. My criteria was "based on tech I know". I don't know Ruby so Jekyll was out. I tried Eleventy and Hexo. I chose Hexo but then ultimately decided I wasn't going to do this new blog.
IIRC, Eleventy printed lots of out-of-date warnings when I installed it and/or the default style was broken in various ways which didn't give me much confidence.
My younger sister asked me to help her start a blog. I just pointed her to substack. Zero effort, easy for her.
I work with Ruby but I never had to use Ruby to use Jekyll. I downloaded the docker image and run it. It checks a host directory for updates and generates the HTML files. It could be written in any other language I don't know.
I don’t have much experience with other SSGs, but I’ve been using Eleventy for my personal site for a few years and I’m a big fan. It’s very simple to get started with, it’s fast to build, it’s powerful and flexible.
I build mine with GitHub Actions and host it free on Pages.
I do custom web dev so am way out of the website hosting game. What are good frameworks now if I want to say, light touch help someone who is slightly technical set up a website? Not full react SPA with an API.
By the sound of your question I will guess you want to make a website for a small or medium sized organization? jQuery is probably the only "framework" you should need.
If they are selling anything on their website, it's probably going to be through a cloud hosted third party service and then it's just an embedded iframe on their website.
If you're making an entire web shop for a very large enterprise or something of similar magnitude, then you have to ask somebody else than me.
jQuery's still the third most used web framework, behind React and before NextJS. If you use jQuery to build Wordpress websites, you'd be specializing in popular web technologies in the year 2025.
There's ways that prevent it -
- Freeze all code after an update through permissions
- Don't make most directories writeable
- Don't allow file uploads, or limit file uploads to media
There's a few plugins that do this, but vanilla WP is dangerous.
I sort of did this with ssh where I figured out how to crash an ssh client that was trying to guess the root password. What I got for my trouble was a number of script kiddies ddosing my poor little server. I switched to just identifying 'bad actors' who are clearly trying to do bad things and just banning their IP with firewall rules. That's becoming more challenging with IPV6 though.
Edit: And for folks who write their own web pages, you can always create zip bombs that are links on a web page that don't show up for humans (white text on white background with no highlight on hover/click anchors). Bots download those things to have a look (so do crawlers and AI scrapers)
> you can always create zip bombs that are links on a web page that don't show up for humans
I did a version of this with my form for requesting an account on my fediverse server. The problem I was having is that there exist these very unsophisticated bots that crawl the web and submit their very unsophisticated spam into every form they see that looks like it might publish it somewhere.
First I added a simple captcha with distorted characters. This did stop many of the bots, but not all of them. Then, after reading the server log, I noticed that they only make three requests in a rapid succession: the page that contains the form, the captcha image, and then the POST request with the form data. They don't load neither the CSS nor the JS.
So I added several more fields to the form and hid them with CSS. Submitting anything in these fields will fail the request and ban your session. I also modified the captcha, I made the image itself a CSS background, and made the src point to a transparent image instead.
And just like that, spam has completely stopped, while real users noticed nothing.
> you can always create zip bombs that are links on a web page that don't show up for humans (white text on white background with no highlight on hover/click anchors)
Automated systems like Cloudflare and stuff also have a list of bot IPs. I was recently setting up a selfhosted VPN and I had to change the IPv4 of the server like 20 times before I got an IP that wasn't banned on half the websites.
You probably want to check how many ips/blocks a provider announces before blocking the entire thing.
It's also not a common metric you can filter on in open firewalls since you must lookup and maintain a cache of IP to ASN, which has to be evicted and updated as blocks still move around.
true, but you can make the link text 'do not click this' or 'not a real link' to let them know. I'm not sure if crawlers have started using LLMs to check pages or not which would be a problem.
Zip bombs are fun. I discovered a vulnerability in a security product once where it wouldn’t properly scan a file for malware if the file was or contained a zip archive greater than a certain size.
The practical effect of this was you could place a zip bomb in an office xml document and this product would pass the ooxml file through even if it contained easily identifiable malware.
Undoubtedly. If you go poking around most any security product (the product I was referring to was not in the EDR space,) you'll see these sorts of issues all over the place.
See https://research.swtch.com/zip for how to make an infinite zip bomb: ie a zip file that unzips to itself, so you can keep unzipping forever without ever hitting bottom.
There was an incident a little while back where some Tor Project anti-censorship infrastructure was run on the same site as a blog post about zip bombs.[0] One of the zip files got crawled by Google, and added to their list of malicious domains, which broke some pretty important parts of Tor's Snowflake tool. Took a couple weeks to get it sorted out.[1]
I deployed this, instead of my usual honeypot script.
It's not working very well.
In the web server log, I can see that the bots are not downloading the whole ten megabyte poison pill.
They are cutting off at various lengths. I haven't seen anything fetch more than around 1.5 Mb of it so far.
Or is it working? Are they decoding it on the fly as a stream, and then crashing? E.g. if something is recorded as having read 1.5 Mb, could it have decoded it to 1.5 Gb in RAM, on the fly, and crashed?
Try content labyrinth. I.e. infinitely generated content with a bunch of references to other generated pages. It may help against simple wget and till bots adapt.
The labyrinth doesn't have to be fast, and things like iocaine (https://iocaine.madhouse-project.org/) don't use much CPU if you don't go and give them something like the Complete Works of Ahakespeare as input (Mine is using Moby Dick), and can easily be constrained with cgroups if you're concerned about resource usage.
I've noticed that LLM scrapers tend to be incredibly patient. They'll wait for minutes for even small amounts of text.
That will be your contribution. If others join scrapping will become very pricey. Till bots become smarter. But then they will not download much of generated crap. Which makes it cheaper for you.
Anyway, from bots perspective labyrinths aren't the main problem. Internet is being flooded with quality LLM-generated content.
Perhaps need to semi-randomize the file size?
I'm guessing some of the bots have a hard limit to the size of the resource they will download.
Many of these are annoying LLM training/scraping bots (in my case anyway).
So while it might not crash them if you spit out a 800KB zipbomb, at least it will waste computing resources on their end.
I currently cannot tell without making a little configuration change, because as soon as an IP address is logged as having visited the trap URL (honeypot, or zipbomb or whatever), a log monitoring script bans that client.
Secondly, I know that most of these bots do not come back. The attacks do not reuse addresses against the same server in order to evade almost any conceivable filter rule that is predicated on a prior visit.
It's worth noting that this is a gzip bomb (acts just like a normal compressed webpage), not a classical zip file that uses nested zips to knock out antiviruses.
Also interested in this. For now I've left a server up for a couple of weeks, went through the logs and set up fail2ban for the most common offenders. Once a month or so I keep checking for offenders but the first iteration already blocked many of them.
It would be a fairly short Perl script to read the access logs and curl a HEAD request to all URLs accessed, printing only those with 200 OK responses.
Here's a start hacked together and tested on my phone:
perl -lnE 'if (/GET ([^ ]+)/ and $p=$1) {
$s=qx(curl -sI https://BASE_URL/$p | head -n 1);
unless ($s =~ /200|302/) {
say $p
}
}'
I protected uploads on one of my applications by creating fixed size temporary disk partitions of like 10MB each and unzipping to those contains the fallout if someone uploads something too big.
Doesn't deal with multi-file ZIP archives. And before you think you can just reject user uploads with multi-file ZIP archives, remember that macOS ZIP files contain the __MACOSX folder with ._ files.
2048 yottabyte Zip Bomb
This zip bomb uses overlapping files and recursion to achieve 7 layers with 256 files each, with the last being a 32GB file.
It is only 266 KB on disk.
When you realise it's a zip bomb it's already too late. Looking at the file size doesn't betray its contents. Maybe applying some heuristics with ClamAV? But even then it's not guaranteed. I think a small partition to isolate decompression is actually really smart. Wonder if we can achieve the same with overlays.
What are you talking about? You get a compressed file. You start decompressing it. When the amount of bytes you've written exceeds some threshold (say 5 megabytes) just stop decompressing, discard the output so far & delete the original file. That is it.
I worked on a commercial HTTP proxy that scanned compressed files. Back then we would start to decompress a file but keep track of the compression ratio. I forget what the cutoff was but as soon as we saw a ratio over a certain threshold we would just mark the file as malicious and block it.
That assumes they're using a stream decompressor library and are feeding that stream manually. Solutions that write the received file to $TMP and just run an external tool (or, say, use sendfile()) don't have the option to abort after N decompressed bytes.
> Solutions that write the received file to $TMP and just run an external tool (or, say, use sendfile()) don't have the option to abort after N decompressed bytes
cgroups with hard-limits will let the external tool's process crash without taking down the script or system along with it.
Depending on the language/library that might not always be possible. For instance python's zip library only provides an extract function, without a way to hook into the decompression process, or limit how much can be written out. Sure, you can probably fork the library to add in the checks yourself, but from a maintainability perspective it might be less work to do with the partition solution.
It also provides an open function for the files in a zip file. I see no reason something like this won't bail after a small limit:
import zipfile
with zipfile.ZipFile("zipbomb.zip") as zip:
for name in zip.namelist():
print("working on " + name)
left = 1000000
with open("dest_" + name, "wb") as fdest, zip.open(name) as fsrc:
while True:
block = fsrc.read(1000)
if len(block) == 0:
break
fdest.write(block)
left -= len(block)
if left <= 0:
print("too much data!")
break
Those files are designed to exhaust the system resources before you can even do these kinds of checks. I'm not particularly familiar with the ins and outs of compression algorithms, but it's intuitively not strange for me to have a a zip that is carefully crafted so that memory and CPU goes out the window before any check can be done. Maybe someone with more experience can give mode details.
I'm sure though that if it was as simples as that we wouldn't even have a name for it.
Not really. It really is that simple. It's just dictionary decompression, and it's just halting it at some limit.
It's just nobody usually implements a limit during decompression because people aren't usually giving you zip bombs. And sometimes you really do want to decompress ginormous files, so limits aren't built in by default.
Your given language might not make it easy to do, but you should pretty much always be able to hack something together using file streams. It's just an extra step is all.
No, compression formats are not Turing-complete. You control the code interpreting the compressed stream and allocating the memory, writing the output, etc. based on what it sees there and can simply choose to return an error after writing N bytes.
Not really. It's easy to abort after exceeding a number of uncompressed bytes or files written. The problem is the typical software for handling these files does not implement restrictions to prevent this.
Seems like a good and simple strategy to me. No real partition needed; tmpfs is cheap on Linux. Maybe OP is using tools that do not easily allow tracking the number of uncompressed bytes.
15+ years ago I fought piracy at a company with very well known training materials for a prestigious certification. I'd distribute zip bombs marked as training material filenames. That was fun.
I do something similar using a script I've cobbled together over the years. Once a year I'll check the 404 logs and add the most popular paths trying to exploit something (ie ancient phpmyadmin vulns) to the shitlist. Requesting 3 of those URLs adds that host to a greylist that only accepts requests to a very limited set of legitimate paths.
I'm curious why a 10GB file of all zeroes would compress only to 10MB. I mean theoretically you could compress it to one byte. I suppose the compression happens on a stream of data instead of analyzing the whole, but I'd assume it would still do better than 10MB.
A compressed file that is only one byte long can only represent maximally 256 different uncompressed files.
Signed, a kid in the 90s who downloaded some "wavelet compression" program from a BBS because it promised to compress all his WaReZ even more so he could then fit moar on his disk. He ran the compressor and hey golly that 500MB ISO fit into only 10MB of disk now! He found out later (after a defrag) that the "compressor" was just hiding data in unused disk sectors and storing references to them. He then learned about Shannon entropy from comp.compression.research and was enlightened.
It has to cater for any possible input. Even with special case handling for this particular (generally uncommon) case of vast runs of the same value: the compressed data will probably be packetized somehow, and each packet can reproduce only so many repeats, so you'll need to repeat each packet enough times to reproduce the output. With 10 GB, it mounts up.
I tried this on my computer with a couple of other tools, after creating a file full of 0s as per the article.
gzip -9 turns it into 10,436,266 bytes in approx 1 minute.
xz -9 turns it into 1,568,052 bytes in approx 4 minutes.
bzip2 -9 turns it into 7,506 (!) bytes in approx 5 minutes.
I think OP should consider getting bzip2 on the case. 2 TBytes of 0s should compress nicely. And I'm long overdue an upgrade to my laptop... you probably won't be waiting long for the result on anything modern.
The reason why the discussion in this thread centers around gzip (and brotli / zstd) is because those are standard compression schemes that HTTP clients will generally support (RFCs 1952, 7932, and 8478).
As far as I can tell, the biggest amplification you can get out of zstd is 32768 times: per the standard, the maximum decompressed block size is 128KiB, and the smallest compressed block is a 3-byte header followed by a 1-byte block (e.g. run-length-encoded). Indeed, compressing a 1GiB file of zeroes yields 32.9KiB of output, which is quite close to that theoretical maximum.
Brotli promises to allow for blocks that decompress up to 16 MiB, so that actually can exceed the compression ratios that bzip2 gives you on that particular input. Compressing that same 1 GiB file with `brotli -9` gives an 809-byte output. If I instead opt for a 16 GiB file (dd if=/dev/zero of=/dev/stdout bs=4M count=4096 | brotli -9 -o zeroes.br), the corresponding output is 12929 bytes, for a compression ratio of about 1.3 million; theoretically this should be able to scale another 2x, but whether that actually plays out in practice is a different matter.
(The best compression for brotli should be available at -q 11, which is the default, but it's substantially slower to compress compared to `brotli -9`. I haven't worked out exactly what the theoretical compression ratio upper bound is for brotli, but it's somewhere between 1.3 and 2.8 million.)
Also note that zstd provides very good compression ratios for its speed, so in practice most use cases benefit from using zstd.
That's a good point, thanks - I was thinking of this from the point of view of the client downloading a file and then trying to examine it, but of course you'd be much better off fucking up their shit at an earlier stage in the pipeline.
Good question. The "ultimate zip bomb" looks something like https://github.com/iamtraction/ZOD - this produces the infamous "42.zip" file, which is about 42KiB, but expands to 3.99 PiB (!).
There's literally no machine on Earth today that can deal with that (as a single file, I mean).
> There's literally no machine on Earth today that can deal with that (as a single file, I mean).
Oh? Certainly not in RAM, but 4 PiB is about 125x 36TiB drives (or 188x 24TiB drives). (You can go bigger if you want to shell out tens of thousands per 100TB SSD, at which point you "only" need 45 of those drives.)
These are numbers such that a purpose-built server with enough SAS expanders could easily fit that within a single rack, for less than $100k (based on the list price of an Exos X24 before even considering any bulk discounts).
No, at least not the ones I am aware of. iirc these kinds of attacks usually targeted content scanners (primarily antivirus). And an AV program would of course have to recursively de compress everything
It'd have to be more than one byte. There's the central directory, zip header, local header then the file itself you need to also tell it how many zeros to make when decompressing the actual file but most compression algorithms don't work like that because they're designed for actual files not essentially blank files so you get larger than the absolute minimum compression.
I mean, if I make a new compression algorithm that says a 10GB file of zeros is represented with a single specific byte, that would technically be compression.
All depends on how much magic you want to shove into an "algorithm"
There probably aren’t any perfectly lossless compression algorithms, I guess? Nothing would ever be all zeroes, so it might not be an edge case accounted for or something? I have no idea, just pulling at strings. Maybe someone smarter can jump in here.
But of course there is. Imagine the following compression scheme:
0-253: output the input byte
254 followed by 0: output 254
254 followed by 1: output 255
255: output 10GB of zeroes
Of course this is an artificial example, but theoretically it's perfectly sound. In fact, I think you could get there with static huffman trees supported by some formats, including gzip.
I get your point(and have no idea why it isn't compressed more), but is the theoretical value of 1 byte correct? With just one single byte, how does it know how big should the file be after being decompressed?
In general, this theoretical problem is called the Kolmogorov Complexity of a string: the size of the smallest program that outputs a the input string, for some definition of "program", e.g., an initial input tape for a given universal turing machine. Unfortunately, Kolmogorov Complexity in general is incomputable, because of the halting problem.
But a gzip decompressor is not turing-complete, and there are no gzip streams that will expand to infinitely large outputs, so it is theoretically possible to find the pseudo-Kolmogorov-Complexity of a string for a given decompressor program by the following algorithm:
Let file.bin be a file containing the input byte sequence.
1. BOUNDS=$(gzip --best -c file.bin | wc -c)
2. LENGTH=1
3. If LENGTH==BOUNDS, run `gzip --best -o test.bin.gz file.bin` and HALT.
4. Generate a file `test.bin.gz` LENGTH bytes long containing all zero bits.
5. Run `gunzip -k test.bin.gz`.
6. If `test.bin` equals `file.bin`, halt.
7. If `test.bin.gz` contains only 1 bits, increment LENGTH and GOTO 3.
8. Replace test.bin.gz with its lexicographic successor by interpreting it as a LENGTH-byte unsigned integer and incrementing it by 1.
9. GOTO 5.
test.bin.gz contains your minimal gzip encoding.
There are "stronger" compressors for popular compression libraries like zlib that outperform the "best" options available, but none of them are this exhaustive because you can surely see how the problem rapidly becomes intractable.
For the purposes of generating an efficient zip bomb, though, it doesn't really matter what the exact contents of the output file are. If your goal is simply to get the best compression ratio, you could enumerate all possible files with that algorithm (up to the bounds established by compressing all zeroes to reach your target decompressed size, which makes a good starting point) and then just check for a decompressed length that meets or exceeds the target size.
I think I'll do that. I'll leave it running for a couple days and see if I can generate a neat zip bomb that beats compressing a stream of zeroes. I'm expecting the answer is "no, the search space is far too large."
I'm an idiot, of course the search space is too large. It outgrows what I can brute force by the heat death of the universe by the time it gets to 16 bytes, even if the "test" is a no-op.
I would need to selectively generate grammatically valid zstd streams for this to be tractable at all.
"But when I detect that they are either trying to inject malicious attacks, or are probing for a response" how are you detecting this? mind sharing some pseudocode?
> knowingly causes the transmission of a program, information, code, or command, and as a result of such conduct, intentionally causes damage without authorization, to a protected computer;
As far as I can tell (again, IANAL) there isn't an exception if you believe said computer is actively attempting to abuse your system[2]. I'm not sure if a zip bomb would constitute intentional damage, but it is at least close enough to the line that I wouldn't feel comfortable risking it.
I don't believe the client counts as a protected computer because they initiated the connection. Also a protected computer is a very specific definition that involves banking and/or commerce and/or the government.
Part B of the definition of "protected computer" says:
> which is used in or affecting interstate or foreign commerce or communication, including a computer located outside the United States that is used in a manner that affects interstate or foreign commerce or communication of the United States
Assuming the server is running in the states, I think that would apply unless the client is in the same state as the server, in which case there is probably similar state law that comes into affect. I don't see anything there that excludes a client, and that makes sense, because otherwise it wouldn't prohibit having a site that tricks people into downloading malware.
The word "accessed" is used multiple times throughout the law. A client accesses a server. A server does not access a client. It responds to a client.
Also, the protected computer has to be involved in commerce. Unless they are accessing the website with the zip bomb using a computer that also is uses for interstate or foreign commerce, it won't qualify.
> The word "accessed" is used multiple times throughout the law.
So what? It isn't in the section I quoted above. I could be wrong, but my reading is that transmitting information that can cause damage with the intent of causing damage is a violation, regardless of if you "access" another system.
> Also, the protected computer has to be involved in commerce
Or communication.
Now, from an ethics standpoint, I don't think there is anything wrong with returning a zipbomb to malicious bots. But I'm not confident enough that doing so is legal that I would risk doing so.
There is IMO no legal use case for an external computer system to initiate a connection with my system without prior legal agreement. It all happens on good will and therefore can be terminated at any time.
There is IMO no legal use case for an external computer system to initiate a connection with my system without prior legal agreement. It all happens on good will.
Just crossed my mind that perhaps lots of bot traffic is coming from botnets of unaware victims who downloaded a shitty game or similar, orchestrated by a malicious C&C server somewhere else. (There was a post about this type of malware recently.) Now, if you crash the victims machine, it’s complicated at least ethically, if not legally.
Well creating a bot is not per se illegal, so assuming the maliciousness-detector on the server isn’t perfect, it could serve the zip bomb to a legitimate bot. And I don’t think it’s crazy that serving zip bombs with the stated intent to sabotage the client would be illegal. But I’m not a lawyer, of course.
Disclosure, I'm not a lawyer either. This is all hypothetical high level discussion here.
> it could serve the zip bomb to a legitimate bot.
Can you define the difference between a legitimate bot, and a non legitimate bot for me ?
The OP didn't mention it, but if we can assume they have SOME form of robots.txt (safe assumtion given their history), would those bots who ignored the robots be considered legitimate/non-legitimate ?
Almost final question, and I know we're not lawyers here, but is there any precedent in case law or anywhere, which defines a 'bad bot' in the eyes of the law ?
Final final question, as a bot, do you believe you have a right or a privilege to scrape a website ?
Mantrapping is a fairly good analogy, and that's very illegal. If the person reading your gas meter gets caught in your mantrap, you're going to prison. You're probably going to prison if somebody burglarizing you gets caught in your mantrap.
Of course their computers will live, but if you accidentally take down your own ISP or maybe some third-party service that you use for something, I'd think they would sue you.
I’m not sure that’s enough, robots.txt isn’t really legally binding so if the zip bomb somehow would be illegal, guarding it behind a robots.txt rule probably wouldn’t make it fine.
Neither is the HTTP specification. Nothing is stopping you from running a Gopher server on TCP port 80, should you get into trouble if it happens to crash a particular crawler?
Making a HTTP request on a random server is like uttering a sentence to a random person in a city: some can be helpful, some may tell you to piss off and some might shank you. If you don't like the latter, then maybe don't go around screaming nonsense loudly to strangers in an unmarked area.
Has any similar case been tried? I'd think that a judge learning the intent of robots.txt and disallow rules is fairly likely to be sympathetic. Seems like it could go either way, I mean. (Jury is probably more a crap-shoot.)
> For the most part, when they do, I never hear from them again. Why? Well, that's because they crash right after ingesting the file.
I would have figured the process/server would restart, and restart with your specific URL since that was the last one not completed.
What makes the bots avoid this site in the future? Are they really smart enough to hard-code a rule to check for crashes and avoid those sites in the future?
Seems like an exponential backoff rule would do the job: I'm sure crashes happen for all sorts of reasons, some of which are bugs in the bot, even on non-adversarial input.
I also had the idea of zip bomb to confuse badly behaved scrapers (and I have mentioned it before to some other people, although I did not implemented it). However, maybe instead of 0x00, you might use a different byte value.
I had other ideas too, but I don't know how well some of them will work (they might depend on what bots they are).
I meant that all of the byte values would be the same (so they would still be repeating), but a different value than zero. However, Brotli could be another idea if the client supports it.
I am ignorant as to how most bots work. Could you have a second line of defense for bots that avoid this bomb: Dynamically generate a file from /dev/random and trickle stream it to them, or would they just keep spawning parallel requests? They would never finish streaming it, and presumably give up at some point. The idea would be to make it more difficult for them to detect it was never going to be valid content.
You want to consider the ratio of your resource consumption to their resource consumption. If you trickle bytes from /dev/random, you are holding open a TCP connection with some minimal overhead, and that's about what they are doing too. Let's assume they are bright enough to use any of the many modern languages or frameworks that can easily handle 10K/100K connections or more on a modern system. They aren't all that bright but certainly some are. You're basically consuming your resources to their resources 1:1. That's not a winning scenario for you.
The gzip bomb means you serve 10MB but they try to consume vast quantities of RAM on their end and likely crash. Much better ratio.
That's clear. It all comes down to their behavior. Will they sit there waiting to finish this download, or just start sending other requests in parallel until you dos yourself? My hope is they would flag the site as low-value and go looking elsewhere, on another site.
For HTTP/1.1 you could send a "chunked" response. Chunked responses are intended to allow the server to start sending dynamically generated content immediately instead of waiting for the generation process to finish before sending. You could just continue to send chunks until the client gives up or crashes.
If the bot is connecting over IPv4, you only have a couple thousand connections before your server starts needing to mess with shared sockets and other annoying connectivity tricks.
I don't think it's a terrible problem to solve these days, especially if you use one of the tarpitting implementations that use nftables/iptables/eBPF, but if you have one of those annoying Chinese bot farms with thousands of IP addresses hitting your server in turn (Huawei likes to do this), you may need to think twice before deploying this solution.
The blog runs on a $6 digital ocean droplet. It's 1GB RAM and 25GB storage. There is a link at the end of the article on how it handles typical HN traffic. Currently at 5% CPU.
There's a lot of creative ideas out there for banning and/or harassing bots. There's tarpits, infinite labyrinths, proof of work || regular challenges, honeypots etc.
Most of the bots I've come across are fairly dumb however, and those are pretty easy to detect & block. I usually use CrowdSec (https://www.crowdsec.net/), and with it you also get to ban the IPs that misbehave on all the other servers that use it before they come to yours. I've also tried turnstile for web pages (https://www.cloudflare.com/application-services/products/tur...) and it seems to work, though I imagine most such products would, as again most bots tend to be fairly dumb.
I'd personally hesitate to do something like serving a zip bomb since it would probably cost the bot farm(s) less than it would cost me, and just banning the IP I feel would serve me better than trying to play with it, especially if I know it's misbehaving.
Edit: Of course, the author could state that the satisfaction of seeing an IP 'go quiet' for a bit is priceless - no arguing against that
It's also cheaper to search Google Images for "Eiffel tower" than booking a flight to Paris and going there, but a lot of people enjoy doing the latter.
I think that's the point, you'd use robots.txt to direct Googlebot/Bingbot/etc away from countermeasures that could potentially mess up your SEO. If other bots ignore the signpost clearly saying not to enter the tarpit, that's their own stupid fault.
This topic comes up from time to time and I'm surprised no one yet mentioned the usual fearmongering rhetoric of zip bombs being potentially illegal.
I'm not a lawyer, but I'm yet to see a real life court case of a bot owner suing a company or an individual for responding to his malicious request with a zip bomb. The usual spiel goes like this: responding to his malicious request with a malicious response makes you a cybercriminal and allows him (the real cybercriminal) to sue you. Again, except of cheap talk I've never heard of a single court case like this. But I can easily imagine them trying to blackmail someone with such cheap threats.
I cannot imagine a big company like Microsoft or Apple using zip bombs, but I fail to see why zip bombs would be considered bad in any way. Anyone with an experience of dealing with malicious bots knows the frustration and the amount of time and money they steal from businesses or individuals.
>On my server, I've added a middleware that checks if the current request is malicious or not.
There's a lot of trust placed in:
>if (ipIsBlackListed() || isMalicious()) {
Can someone assigned a previously blacklisted IP or someone who uses a tool to archive the website that mimics a bot be served malware? Is the middleware good enough or "good enough so far"?
Close enough to 100% of my internet traffic flows through a VPN. I have been blacklisted by various services upon connecting to a VPN or switching servers on multiple occasions.
Mildly amusing, but it seems like this is thinking that two wrongs make a right, so let us serve malware instead of using a WAF or some other existing solution to the bot problem.
The web is overrun by malicious actors without any sense of morality. Since playing by the rules is clearly not working, I'm in favor of doing anything in my power to waste their resources. I would go a step further and try to corrupt their devices so that they're unable to continue their abuse, but since that would require considerably more effort from my part, a zip bomb is a good low-effort solution.
Based on the example in the post, that thinking might need to be extended to "someone happening to be using a blocklisted IP." I don't serve up zip bombs, but I've blocklisted many abusive bots using VPN IPs over the years which have then impeded legitimate users of the same VPNs.
At least, not with the default rules. I read that discussion a few days ago and was surprised how few callouts there were that a WAF is just a part of the infrastructure - it is the rules that people are actually complaining about. I think the problem is that so many apps run on AWS and their default WAF rules have some silly content filtering. And their "security baseline" says that you have to use a WAF and include their default rules, so security teams lock down on those rules without any real thought put into whether or not they make sense for any given scenario.
So first, let me prefix this by saying I generally don't accept cookies from websites I don't explicitly first allow, my reasoning being "why am I granting disk read/write access to [mostly] shady actors to allow them to track me?"
(I don't think your blog qualifies as shady … but you're not in my allowlist, either.)
So if I visit https://anubis.techaro.lol/ (from the "Anubis" link), I get an infinite anime cat girl refresh loop — which honestly isn't the worst thing ever?
Neither xeserv.us nor techaro.lol are in my allowlist. Curious that one seems to pass. IDK.
The blog post does have that lovely graph … but I suspect I'll loop around the "no cookie" loop in it, so the infinite cat girls are somewhat expected.
I was working on an extension that would store cookies very ephemerally for the more malicious instances of this, but I think its design would work here too. (In-RAM cookie jar, burns them after, say, 30s. Persisted long enough to load the page.)
Just FYI temporary containers (Firefox extension) seem to be the solution you're looking for. It essentially generates a new container for every tab you open (subtabs can be either new containers or in the same container). Once the tab is closed it destroys the container and deletes all browsing data (including cookies). You can still whitelist some domains to specific persistent containers.
I used cookie blockers for a long time, but always ended up having to whitelist some sites even though I didn't want their cookies because the site would misbehave without them. Now I just stopped worrying.
I admire your deontological zealotry. That said, I think there is an implied virtuous aspect of "internet vigilantism" that feels ignored (i.e. disabling a malicious bot means it does not visit other sites) While I do not absolve anyone from taking full responsibility for their actions, I have a suspicion that terrorists do a bit more than just avert a greater wrong--otherwise, please sign me up!
Once upon a time around 2001 or so I used to have a static line at home and host some stuff on my home linux box. A windows NT update had meant a lot of them had enabled this optimistic encryption thing where windows boxes would try to connect to a certain port and negotiate an s/wan before doing TCP traffic. I was used to seeing this traffic a lot on my firewall so no big deal. However there was one machine in particular that was really obnoxious. It would try to connect every few seconds and would just not quit.
I tried to contact the admin of the box (yeah that’s what people used to do) and got nowhere. Eventually I sent a message saying “hey I see your machine trying to connect every few seconds on port <whatever it is>. I’m just sending a heads up that we’re starting a new service on that port and I want to make sure it doesn’t cause you any problems.”
Of course I didn’t hear back. Then I set up a server on that port that basically read from /dev/urandom, set TCP_NODELAY and a few other flags and pushed out random gibberish as fast as possible. I figured the clients of this service might not want their strings of randomness to be null-terminated so I thoughtfully removed any nulls that might otherwise naturally occur. The misconfigured NT box connected, drank 5 seconds or so worth of randomness, then disappeared. Then 5 minutes later, reappeared, connected, took its buffer overflow medicine and disappeared again. And this pattern then continued for a few weeks until the box disappeared from the internet completely.
I like to imagine that some admin was just sitting there scratching his head wondering why his NT box kept rebooting.
The lesson for any programmers reading this is to always set an upper limit for how much data you accept from someone else. Every request should have both a timeout and a limit on the amounts of data it will consume.
That doesn't necessarily need to be in the request itself.
You can also limit the wider process or system your request is part of.
I enjoyed reading this, thank you for sharing. When you say you tried to contact the admin of the box and that this was common back then, how would you typically find the contact info for an arbitrary client's admin?
You can also find out who owns a general group of IP addresses, and at the time they would often assist you in further pinpointing who is responsible for a particular address.
tech-c / abuse addresses were commonly available on whois.
That’s awesome! Thank you for sharing.
Back when I was a stupid kid, I once did
on my home page as a joke. Browsers at the time didn’t like that, they basically froze, sometimes taking the client system down with them.Later on, browsers started to check for actual content I think, and would abort such requests.
I made a 64kx64k JPEG once by feeding the encoder the same line of macro blocks until it produce the entire image.
Years later I was finally able to open it.
I had a ton of trouble opening a 10MB or so png a few weeks back. It was stitched together screenshots forming a map of some areas in a game, so it was quite large. Some stuff refused to open it at all as if the file was invalid, some would hang for minutes, some opened blurry. My first semi-success was Fossify Gallery on my phone from F-Droid. If I let it chug a bit, it'd show a blurry image, a while longer it'd focus. Then I'd try to zoom or pan and it'd blur for ages again. I guess it was aggressively lazy-loading. What worked in the end was GIMP. I had the thought that the image was probably made in an editor, so surely an editor could open it. The catch is that it took like 8GB of RAM, but then I could see clearly, zoom, and pan all I wanted. It made me wonder why there's not an image viewer that's just the viewer part of GIMP or something.
Among things that didn't work were qutebrowser, icecat, nsxiv, feh, imv, mpv. I did worry at first the file was corrupt, I was redownloading it, comparing hashes with a friend, etc. Makes for an interesting benchmark, I guess.
For others curious, here's the file: https://0x0.st/82Ap.png
I'd say just curl/wget it, don't expect it to load in a browser.
That's a 36,000x20,000 PNG, 720 megapixels. Many decoders explicitly limit the maximum image area they'll handle, under the reasonable assumption that it will exceed available RAM and take too long, and assume the file was crafted maliciously or by mistake.
PDF files with included vector-based layers, e.g. plans or maps of large area, are also quite difficult to render/open.
Firefox on a mid-tier Samsung and a cheapo data connection (4G) took avout 30s to load. I could pan, but it limited me from zooming much, and the little I could zoom in looked quite blury.
On Firefox on Android on my pretty old phone, a blurry preview rendered in about 10 seconds, and it was fully rendered in 20 something seconds. Smooth panning and zooming the entire time
Firefox on a Samsung S23 Ultra did it a few seconds faster but otherwise the same experience
It loads in about 5 seconds on an iPhone 12 using safari.
It also pans and zooms swiftly
I use honey view for reading comics etc. It can handle this.
Old school acdsee would have been fine too.
I think it's all the pixel processing on the modern image viewers (or they're just using system web views that isn't 100% just a straight render).
I suspect that the more native renderers are doing some extra magic here. Or just being significantly more OK with using up all your ram.
ImgurViewer from fdroid on an FP5 opened it blurry after around 5s and 5s later it was rendered completely.
Pan&zoom works instantly with a blurry preview and then takes another 5-10s to render completely.
IrfanView was able to load it in about 8 seconds (Ryzen 7 5800x) using 2.8GB of RAM, but zooming/panning is quite slow (~500ms per action)
IrfanView on my PC is very fast. Zoomed to 100% I can pan around no problem. Is it using CPU or GPU? I've got an 11900K CPU and RTX 3090.
For what it's worth, this loaded (slowly) in Firefox on Windows for me (but zooming was blurry), and the default Photos viewer opened it no problem with smooth zooming and panning.
Safari on my MacBook Air opened it fine, though it took about four seconds. Zooming works fine as well. It does take ~3GB of memory according to Activity Monitor.
Interestingly enough, it loads in about 5 seconds on my Pixel 6a.
It loaded after 10-15 seconds on myiPad Pro M1, although it did start reloading after I looked around in it.
It loads in about 10 seconds in Safari on an M1 Air. I think I am spoiled.
I once encoded an entire TV OP into a multi-megabyte animated cursor (.ani) file.
Surprisingly, Windows 95 didn't die trying to load it, but quite a lot of operations in the system took noticeably longer than they normally did.
I hope you weren’t paying for bandwidth by the KiB.
Nah, back then we paid for bandwidth by the kb.
That’s even worse! :)
Sounds like the favicon.ico that would crash the browser.
I think this was it:
https://freedomhacker.net/annoying-favicon-crash-bug-firefox...
Looks like something I should add for my web APIs which are to be queried only by clients aware of the API specification.
Devide by zero happens to everyone eventually.
https://medium.com/@bishr_tabbaa/when-smart-ships-divide-by-...
"On 21 September 1997, the USS Yorktown halted for almost three hours during training maneuvers off the coast of Cape Charles, Virginia due to a divide-by-zero error in a database application that propagated throughout the ship’s control systems."
" technician tried to digitally calibrate and reset the fuel valve by entering a 0 value for one of the valve’s component properties into the SMCS Remote Database Manager (RDM)"
Bad bot
I remember reading about that some years ago. It involved Windows NT.
https://www.google.com/search?q=windows+nt+bug+affects+ship
These days, almost all browsers accept zstd and brotli, so these bombs can be even more effective today! [This](https://news.ycombinator.com/item?id=23496794) old comment showed an impressive 1.2M:1 compression ratio and [zstd seems to be doing even better](https://github.com/netty/netty/issues/14004).
Though, bots may not support modern compression standards. Then again, that may be a good way to block bots: every modern browser supports zstd, so just force that on non-whitelisted browser agents and you automatically confuse scrapers.
If you nest the gzip inside another gzip it gets even smaller since the blocks of compressed '0' data are themselves low entropy in the first generation gzip. Nested zst reduces the 10G file to 99 bytes.
Can you hand edit to create recursive file structures to make it infinite? I used to use debug in dos to make what appeared to be gigantic floppy discs by editing the fat
That's what I was hoping for with the original article.
Wouldnt that defeat the attack though as you arent serving the large content anymore
It would need a bot that is accessing files via hyperlink with an aim to decompress them and riffle through their contents. The compressed file can be delivered over a compressed response to achieve the two layers, cutting down significantly on the outbound traffic. passwd.zst, secrets.docx, etc. would look pretty juicy. Throw some bait in honeypot directories (exposed for file access) listed in robots.txt and see who takes it.
How will my browser react on receiving such bombs? I’d rather not to test it myself…
> At my old employer, a bot discovered a wordpress vulnerability and inserted a malicious script into our server
I know it's slightly off topic, but it's just so amusing (edit: reassuring) to know I'm not the only one who, after 1 hour of setting up Wordpress there's a PHP shell magically deployed on my server.
>Take over a wordpress site for a customer
>Oh look 3 separate php shells with random strings as a name
Never less than 3, but always guaranteed.
Yes, never self host Wordpress if you value your sanity. Even if it’s not the first hour it will eventually happen when you forget a patch.
Hosting WordPress myself for 13 years now and have no problem :) Just follow standard security practices and don't install gazillion plugins.
There's a lot of essential functionality missing from WordPress, meaning you have to install plugins. Depending on what you need to do.
But it's such a bad platform that there really isn't any reason for anybody to use WordPress for anything. No matter your use case, there will be a better alternative to WordPress.
Can you recommend an alternative for a non-technical organization, where there's someone who needs to be able to edit pages and upload documents on a regular basis, so they need as user-friendly an interface as possible for that? Especially when they don't have a budget for it, and you're helping them out as a favor? It's so easy to spin up Wordpress for them, but I'm not a fan either.
I've tried Drupal in the past for such situations, but it was too complicated for them. That was years ago, so maybe it's better now.
I find it very telling that there's no 2 responses to this post recommending the same thing. Confirms my belief that there is no real alternative to Wordpress for a free and open-source CMS that is straightforward to install and usable to build and edit pages by non-tech-experts.
Perhaps people who wanted to recommend the same thing as was already written, just upvoted instead of writing their own comment?
DrupalCMS is a new project that aims to radically simplify for end users https://new.drupal.org/drupal-cms
> Can you recommend an alternative for a non-technical organization, where there's someone who needs to be able to edit pages and upload documents on a regular basis, so they need as user-friendly an interface as possible for that
25 years ago we used Microsoft Frontpage for that, with the web root mapped to a file share that the non-technical secretary could write to and edit it as if it were a word processor.
Somehow I feel we have regressed from that simplicity, with nothing but hand waving to make up for it. This method was declared "obsolete" and ... Wordpress kludges took its place as somehow "better". Someone prove me wrong.
A previous workplace of mine did the same with Netscape (and later, Mozilla) Composer. Users could modify content via WebDAV.
We’re developing https://bluocms.com/
- very hard to hack because we pre render all assets to a Cloudflare kv store
- public website and CMS editor are on different domains
Basically very hard to hack. Also as a bonus is much more reliable as it will only go down when Cloudflare does.
I've had some luck using Decap for that. An initial dev setup, followed by almost never needing support from the PR team running it.
[0] https://decapcms.org/
Statamic https://statamic.com/
Seconded. It's absolutely phenomenal as a headful or headless CMS.
Yes I can. There's an excellent and stable solution called SurrealCMS, made by an indie developer. You connect it by FTP to any traditional web design (HTML+CSS+JS), and the users get a WYSIWYG editor where the published output looks exactly as it looked when editing. It's dirt cheap at $9 per month.
Edit: I actually feel a bit sorry for the SurrealCMS developer. He has a fantastic product that should be an industry standard, but it's fairly unknown.
Static site with Jekyll?
Jekyll and other static site generators do not repo Wordpress any more than notepad repos MSWord
In one, multiple users can login, edit WYSIWYG, preview, add images, etc, all from one UI. You can access it from any browser including smart phones and tablets.
In the other, you get to instruct users on git, how to deal with merge conflicts, code review (two people can't easily work on a post like they can in wordpress), previews require a manual build, you need a local checkout and local build installation to do the build. There no WYSIWYG, adding images is a manual process of copying a file, figuring out the URL, etc... No smartphone/tablet support. etc....
I switched by blog from wordpress install to a static site geneator because I got tired of having to keep it up to date but my posting dropped because of friction of posting went way up. I could no longer post from a phone. I couldn't easily add images. I had to build to preview. And had to submit via git commits and pushes. All of that meant what was easy became tedious.
Have you checked static site CMSes?
For example (not affiliated with them) https://www.siteleaf.com/
what are your favorite static site generators? I googled it and cloudflare article came up with Jekyll,Gatsby,Hugo,Next.js, Eleventy. But would like to avoid doing research if can be helped on pros/cons of each.
I looked recently when thinking of starting some new shared blog. My criteria was "based on tech I know". I don't know Ruby so Jekyll was out. I tried Eleventy and Hexo. I chose Hexo but then ultimately decided I wasn't going to do this new blog.
IIRC, Eleventy printed lots of out-of-date warnings when I installed it and/or the default style was broken in various ways which didn't give me much confidence.
My younger sister asked me to help her start a blog. I just pointed her to substack. Zero effort, easy for her.
I work with Ruby but I never had to use Ruby to use Jekyll. I downloaded the docker image and run it. It checks a host directory for updates and generates the HTML files. It could be written in any other language I don't know.
I don’t have much experience with other SSGs, but I’ve been using Eleventy for my personal site for a few years and I’m a big fan. It’s very simple to get started with, it’s fast to build, it’s powerful and flexible.
I build mine with GitHub Actions and host it free on Pages.
Jekyll and GitHub pages go together pretty well.
I do custom web dev so am way out of the website hosting game. What are good frameworks now if I want to say, light touch help someone who is slightly technical set up a website? Not full react SPA with an API.
By the sound of your question I will guess you want to make a website for a small or medium sized organization? jQuery is probably the only "framework" you should need.
If they are selling anything on their website, it's probably going to be through a cloud hosted third party service and then it's just an embedded iframe on their website.
If you're making an entire web shop for a very large enterprise or something of similar magnitude, then you have to ask somebody else than me.
Does anyone actually still use jQuery?
Everything I've built in the past like 5 years has been almost entirely pure ES6 with some helpers like jsviews.
jQuery's still the third most used web framework, behind React and before NextJS. If you use jQuery to build Wordpress websites, you'd be specializing in popular web technologies in the year 2025.
https://survey.stackoverflow.co/2024/technology#1-web-framew...
Sure, why not? It's lightweight and works well, and there's a lot of good solutions that you can find already made for you online.
jQuery hasn’t been necessary for many years. Vanilla JS equivalents of jQuery code are well-supported.
https://youmightnotneedjquery.com/
The vanilla one is so much longer.
Never use that junk if you value your sanity, I think you mean.
Ditto to self-hosting wordpress works fine with standard hosting practices and not installing a bazillion random plugins.
>after 1 hour
I've used this teaching folks devops, here deploy your first hello world nginx server... huh what are those strange requests in the log?
There's ways that prevent it - - Freeze all code after an update through permissions - Don't make most directories writeable - Don't allow file uploads, or limit file uploads to media
There's a few plugins that do this, but vanilla WP is dangerous.
I sort of did this with ssh where I figured out how to crash an ssh client that was trying to guess the root password. What I got for my trouble was a number of script kiddies ddosing my poor little server. I switched to just identifying 'bad actors' who are clearly trying to do bad things and just banning their IP with firewall rules. That's becoming more challenging with IPV6 though.
Edit: And for folks who write their own web pages, you can always create zip bombs that are links on a web page that don't show up for humans (white text on white background with no highlight on hover/click anchors). Bots download those things to have a look (so do crawlers and AI scrapers)
> you can always create zip bombs that are links on a web page that don't show up for humans
I did a version of this with my form for requesting an account on my fediverse server. The problem I was having is that there exist these very unsophisticated bots that crawl the web and submit their very unsophisticated spam into every form they see that looks like it might publish it somewhere.
First I added a simple captcha with distorted characters. This did stop many of the bots, but not all of them. Then, after reading the server log, I noticed that they only make three requests in a rapid succession: the page that contains the form, the captcha image, and then the POST request with the form data. They don't load neither the CSS nor the JS.
So I added several more fields to the form and hid them with CSS. Submitting anything in these fields will fail the request and ban your session. I also modified the captcha, I made the image itself a CSS background, and made the src point to a transparent image instead.
And just like that, spam has completely stopped, while real users noticed nothing.
I did essentially the same thing. I have this input in a form:
With this CSS: And any form submission with a value set for the email is blocked. It stopped 100% of the spam I was getting.We use to just call those honeypot fields. Works like a charm.
Oh that is great.
> you can always create zip bombs that are links on a web page that don't show up for humans (white text on white background with no highlight on hover/click anchors)
RIP screen reader users?
“aria-hidden” would spare those users, and possibly be ignored by the bots unless they are sophisticated.
Check this out if you want to stop this behavior...
https://github.com/skeeto/endlessh
Automated systems like Cloudflare and stuff also have a list of bot IPs. I was recently setting up a selfhosted VPN and I had to change the IPv4 of the server like 20 times before I got an IP that wasn't banned on half the websites.
I am just banning large swaths of IPs. Banning most of Asia and the middle east reduced the amount of bad traffic by something like 98%.
Why is it harder to firewall them with IPv6? I seems this would be the easier of the two to firewall.
Manual banning is about the same since you just book /56 or bigger, entire providers or countries.
Automated banning is harder, you'd probably want a heuristic system and look up info on IPs.
IPv4 with NAT means you can "overban" too.
Why wouldn't something like fail2ban not work here? That's what it's built for and has been around for eons.
I think they are suggesting the range of IPs to block is too high?
Allow -> Tarpit -> Block should be done by ASN
You probably want to check how many ips/blocks a provider announces before blocking the entire thing.
It's also not a common metric you can filter on in open firewalls since you must lookup and maintain a cache of IP to ASN, which has to be evicted and updated as blocks still move around.
Maybe it’s easier to circumvent because getting a new IPv6 address is easier than with IPv4?
These links do show up for humans who might be using text browsers, (perhaps) screen readers, bookmarklets that list the links on a page, etc.
true, but you can make the link text 'do not click this' or 'not a real link' to let them know. I'm not sure if crawlers have started using LLMs to check pages or not which would be a problem.
Zip bombs are fun. I discovered a vulnerability in a security product once where it wouldn’t properly scan a file for malware if the file was or contained a zip archive greater than a certain size.
The practical effect of this was you could place a zip bomb in an office xml document and this product would pass the ooxml file through even if it contained easily identifiable malware.
Eh I got news for ya.
The file size problem is still an issue for many big name EDRs.
Undoubtedly. If you go poking around most any security product (the product I was referring to was not in the EDR space,) you'll see these sorts of issues all over the place.
It have to be the way it is.
Scanning them are resources intensive. The choice are (1) skip scanning them; (2) treat them as malware; (3) scan them and be DoS'ed.
(deferring the decision to human iss effectively DoS'ing your IT support team)
Option #4, detect the zip bomb in its compressed form, and skip over that section of the file. Just like the malware ignores the zip bomb.
Just the fact that it contains a zip bomb makes it malware by itself.
is that endpoint detection and response?
See https://research.swtch.com/zip for how to make an infinite zip bomb: ie a zip file that unzips to itself, so you can keep unzipping forever without ever hitting bottom.
There was an incident a little while back where some Tor Project anti-censorship infrastructure was run on the same site as a blog post about zip bombs.[0] One of the zip files got crawled by Google, and added to their list of malicious domains, which broke some pretty important parts of Tor's Snowflake tool. Took a couple weeks to get it sorted out.[1]
[0] https://www.bamsoftware.com/hacks/zipbomb/ [1] https://www.bamsoftware.com/hacks/zipbomb/#safebrowsing
I deployed this, instead of my usual honeypot script.
It's not working very well.
In the web server log, I can see that the bots are not downloading the whole ten megabyte poison pill.
They are cutting off at various lengths. I haven't seen anything fetch more than around 1.5 Mb of it so far.
Or is it working? Are they decoding it on the fly as a stream, and then crashing? E.g. if something is recorded as having read 1.5 Mb, could it have decoded it to 1.5 Gb in RAM, on the fly, and crashed?
There is no way to tell.
Try content labyrinth. I.e. infinitely generated content with a bunch of references to other generated pages. It may help against simple wget and till bots adapt.
PS: I'm on the bots side, but don't mind helping.
This doesn't work if you pay bandwidth and CPU usage for your servers though.
The labyrinth doesn't have to be fast, and things like iocaine (https://iocaine.madhouse-project.org/) don't use much CPU if you don't go and give them something like the Complete Works of Ahakespeare as input (Mine is using Moby Dick), and can easily be constrained with cgroups if you're concerned about resource usage.
I've noticed that LLM scrapers tend to be incredibly patient. They'll wait for minutes for even small amounts of text.
That will be your contribution. If others join scrapping will become very pricey. Till bots become smarter. But then they will not download much of generated crap. Which makes it cheaper for you.
Anyway, from bots perspective labyrinths aren't the main problem. Internet is being flooded with quality LLM-generated content.
Wouldn't this just waste your own bandwidth/resources?
Perhaps need to semi-randomize the file size? I'm guessing some of the bots have a hard limit to the size of the resource they will download.
Many of these are annoying LLM training/scraping bots (in my case anyway). So while it might not crash them if you spit out a 800KB zipbomb, at least it will waste computing resources on their end.
Do they comeback? If so then they detect it and avoid it. If not then they crashed and mission accomplished.
I currently cannot tell without making a little configuration change, because as soon as an IP address is logged as having visited the trap URL (honeypot, or zipbomb or whatever), a log monitoring script bans that client.
Secondly, I know that most of these bots do not come back. The attacks do not reuse addresses against the same server in order to evade almost any conceivable filter rule that is predicated on a prior visit.
It's worth noting that this is a gzip bomb (acts just like a normal compressed webpage), not a classical zip file that uses nested zips to knock out antiviruses.
Is there a list of popular attack vector urls located somewhere? I want to just auto-ban anyone sniffing for .env or ../../../../ etc.
Rather not write it myself
Also interested in this. For now I've left a server up for a couple of weeks, went through the logs and set up fail2ban for the most common offenders. Once a month or so I keep checking for offenders but the first iteration already blocked many of them.
It would be a fairly short Perl script to read the access logs and curl a HEAD request to all URLs accessed, printing only those with 200 OK responses.
Here's a start hacked together and tested on my phone:
I protected uploads on one of my applications by creating fixed size temporary disk partitions of like 10MB each and unzipping to those contains the fallout if someone uploads something too big.
`unzip -p | head -c 10MB`
Doesn't deal with multi-file ZIP archives. And before you think you can just reject user uploads with multi-file ZIP archives, remember that macOS ZIP files contain the __MACOSX folder with ._ files.
What? You partitioned a disk rather than just not decompressing some comically large file?
https://github.com/uint128-t/ZIPBOMB
When you realise it's a zip bomb it's already too late. Looking at the file size doesn't betray its contents. Maybe applying some heuristics with ClamAV? But even then it's not guaranteed. I think a small partition to isolate decompression is actually really smart. Wonder if we can achieve the same with overlays.What are you talking about? You get a compressed file. You start decompressing it. When the amount of bytes you've written exceeds some threshold (say 5 megabytes) just stop decompressing, discard the output so far & delete the original file. That is it.
I worked on a commercial HTTP proxy that scanned compressed files. Back then we would start to decompress a file but keep track of the compression ratio. I forget what the cutoff was but as soon as we saw a ratio over a certain threshold we would just mark the file as malicious and block it.
That assumes they're using a stream decompressor library and are feeding that stream manually. Solutions that write the received file to $TMP and just run an external tool (or, say, use sendfile()) don't have the option to abort after N decompressed bytes.
> Solutions that write the received file to $TMP and just run an external tool (or, say, use sendfile()) don't have the option to abort after N decompressed bytes
cgroups with hard-limits will let the external tool's process crash without taking down the script or system along with it.
> cgroups with hard-limits
This is exactly the same idea as partitioning, though.
Depending on the language/library that might not always be possible. For instance python's zip library only provides an extract function, without a way to hook into the decompression process, or limit how much can be written out. Sure, you can probably fork the library to add in the checks yourself, but from a maintainability perspective it might be less work to do with the partition solution.
It also provides an open function for the files in a zip file. I see no reason something like this won't bail after a small limit:
That is exactly what OP is doing, they've just implemented it at the operating system/file system level.
Those files are designed to exhaust the system resources before you can even do these kinds of checks. I'm not particularly familiar with the ins and outs of compression algorithms, but it's intuitively not strange for me to have a a zip that is carefully crafted so that memory and CPU goes out the window before any check can be done. Maybe someone with more experience can give mode details.
I'm sure though that if it was as simples as that we wouldn't even have a name for it.
Not really. It really is that simple. It's just dictionary decompression, and it's just halting it at some limit.
It's just nobody usually implements a limit during decompression because people aren't usually giving you zip bombs. And sometimes you really do want to decompress ginormous files, so limits aren't built in by default.
Your given language might not make it easy to do, but you should pretty much always be able to hack something together using file streams. It's just an extra step is all.
Isn’t this basically a question about the halting problem? Whatever arbitrary cutoff you chose might not work for all.
No, compression formats are not Turing-complete. You control the code interpreting the compressed stream and allocating the memory, writing the output, etc. based on what it sees there and can simply choose to return an error after writing N bytes.
Yes, and even if they were Turing complete, you could still run your Turing-machine-equivalent for n steps only before bailing.
Not really. It's easy to abort after exceeding a number of uncompressed bytes or files written. The problem is the typical software for handling these files does not implement restrictions to prevent this.
damn, it broke the macOS archiver utility.
Seems like a good and simple strategy to me. No real partition needed; tmpfs is cheap on Linux. Maybe OP is using tools that do not easily allow tracking the number of uncompressed bytes.
Yes I'd rather deal with a simple out of disk space error than perform some acrobatics to "safely" unzip a potential zip bomb.
Also zip bombs are not comically large until you unzip them.
Also you can just unpack any sort of compressed file format without giving any thought to whether you are handling it safely.
15+ years ago I fought piracy at a company with very well known training materials for a prestigious certification. I'd distribute zip bombs marked as training material filenames. That was fun.
I do something similar using a script I've cobbled together over the years. Once a year I'll check the 404 logs and add the most popular paths trying to exploit something (ie ancient phpmyadmin vulns) to the shitlist. Requesting 3 of those URLs adds that host to a greylist that only accepts requests to a very limited set of legitimate paths.
Attacked Over Tor [2017]
https://www.hackerfactor.com/blog/index.php?/archives/762-At...
I'm curious why a 10GB file of all zeroes would compress only to 10MB. I mean theoretically you could compress it to one byte. I suppose the compression happens on a stream of data instead of analyzing the whole, but I'd assume it would still do better than 10MB.
A compressed file that is only one byte long can only represent maximally 256 different uncompressed files.
Signed, a kid in the 90s who downloaded some "wavelet compression" program from a BBS because it promised to compress all his WaReZ even more so he could then fit moar on his disk. He ran the compressor and hey golly that 500MB ISO fit into only 10MB of disk now! He found out later (after a defrag) that the "compressor" was just hiding data in unused disk sectors and storing references to them. He then learned about Shannon entropy from comp.compression.research and was enlightened.
> He found out later (after a defrag) that the "compressor" was just hiding data in unused disk sectors and storing references to them
So you could access the files until you wrote more data to disk?
Strange to think that is approach would actually work pretty damn well for most people because most people aren’t using therefore hard drive space
man, a comment that brings back memories. you and me both.
It has to cater for any possible input. Even with special case handling for this particular (generally uncommon) case of vast runs of the same value: the compressed data will probably be packetized somehow, and each packet can reproduce only so many repeats, so you'll need to repeat each packet enough times to reproduce the output. With 10 GB, it mounts up.
I tried this on my computer with a couple of other tools, after creating a file full of 0s as per the article.
gzip -9 turns it into 10,436,266 bytes in approx 1 minute.
xz -9 turns it into 1,568,052 bytes in approx 4 minutes.
bzip2 -9 turns it into 7,506 (!) bytes in approx 5 minutes.
I think OP should consider getting bzip2 on the case. 2 TBytes of 0s should compress nicely. And I'm long overdue an upgrade to my laptop... you probably won't be waiting long for the result on anything modern.
The reason why the discussion in this thread centers around gzip (and brotli / zstd) is because those are standard compression schemes that HTTP clients will generally support (RFCs 1952, 7932, and 8478).
As far as I can tell, the biggest amplification you can get out of zstd is 32768 times: per the standard, the maximum decompressed block size is 128KiB, and the smallest compressed block is a 3-byte header followed by a 1-byte block (e.g. run-length-encoded). Indeed, compressing a 1GiB file of zeroes yields 32.9KiB of output, which is quite close to that theoretical maximum.
Brotli promises to allow for blocks that decompress up to 16 MiB, so that actually can exceed the compression ratios that bzip2 gives you on that particular input. Compressing that same 1 GiB file with `brotli -9` gives an 809-byte output. If I instead opt for a 16 GiB file (dd if=/dev/zero of=/dev/stdout bs=4M count=4096 | brotli -9 -o zeroes.br), the corresponding output is 12929 bytes, for a compression ratio of about 1.3 million; theoretically this should be able to scale another 2x, but whether that actually plays out in practice is a different matter.
(The best compression for brotli should be available at -q 11, which is the default, but it's substantially slower to compress compared to `brotli -9`. I haven't worked out exactly what the theoretical compression ratio upper bound is for brotli, but it's somewhere between 1.3 and 2.8 million.)
Also note that zstd provides very good compression ratios for its speed, so in practice most use cases benefit from using zstd.
That's a good point, thanks - I was thinking of this from the point of view of the client downloading a file and then trying to examine it, but of course you'd be much better off fucking up their shit at an earlier stage in the pipeline.
Good question. The "ultimate zip bomb" looks something like https://github.com/iamtraction/ZOD - this produces the infamous "42.zip" file, which is about 42KiB, but expands to 3.99 PiB (!).
There's literally no machine on Earth today that can deal with that (as a single file, I mean).
That's far from the ultimate zip bomb.
42.zip has five layers. But you can make a zip file that has an infinite number of layers. See https://research.swtch.com/zip or https://alf.nu/ZipQuine
> There's literally no machine on Earth today that can deal with that (as a single file, I mean).
Oh? Certainly not in RAM, but 4 PiB is about 125x 36TiB drives (or 188x 24TiB drives). (You can go bigger if you want to shell out tens of thousands per 100TB SSD, at which point you "only" need 45 of those drives.)
These are numbers such that a purpose-built server with enough SAS expanders could easily fit that within a single rack, for less than $100k (based on the list price of an Exos X24 before even considering any bulk discounts).
Do must unzip programs work recursively by default?
No, at least not the ones I am aware of. iirc these kinds of attacks usually targeted content scanners (primarily antivirus). And an AV program would of course have to recursively de compress everything
It'd have to be more than one byte. There's the central directory, zip header, local header then the file itself you need to also tell it how many zeros to make when decompressing the actual file but most compression algorithms don't work like that because they're designed for actual files not essentially blank files so you get larger than the absolute minimum compression.
I mean, if I make a new compression algorithm that says a 10GB file of zeros is represented with a single specific byte, that would technically be compression.
All depends on how much magic you want to shove into an "algorithm"
If it's not standard I count the extra program required to decompress it as part of the archive.
Yes, though in this case that wouldn't add much.
There probably aren’t any perfectly lossless compression algorithms, I guess? Nothing would ever be all zeroes, so it might not be an edge case accounted for or something? I have no idea, just pulling at strings. Maybe someone smarter can jump in here.
No lossless algorithm can compress all strings; some will end up larger. This is a consequence of the pigeonhole principle.
It requires at leadt few bytes, there is no way to represent 10GB of data in 8 bits.
But of course there is. Imagine the following compression scheme:
Of course this is an artificial example, but theoretically it's perfectly sound. In fact, I think you could get there with static huffman trees supported by some formats, including gzip.I get your point(and have no idea why it isn't compressed more), but is the theoretical value of 1 byte correct? With just one single byte, how does it know how big should the file be after being decompressed?
In general, this theoretical problem is called the Kolmogorov Complexity of a string: the size of the smallest program that outputs a the input string, for some definition of "program", e.g., an initial input tape for a given universal turing machine. Unfortunately, Kolmogorov Complexity in general is incomputable, because of the halting problem.
But a gzip decompressor is not turing-complete, and there are no gzip streams that will expand to infinitely large outputs, so it is theoretically possible to find the pseudo-Kolmogorov-Complexity of a string for a given decompressor program by the following algorithm:
Let file.bin be a file containing the input byte sequence.
1. BOUNDS=$(gzip --best -c file.bin | wc -c)
2. LENGTH=1
3. If LENGTH==BOUNDS, run `gzip --best -o test.bin.gz file.bin` and HALT.
4. Generate a file `test.bin.gz` LENGTH bytes long containing all zero bits.
5. Run `gunzip -k test.bin.gz`.
6. If `test.bin` equals `file.bin`, halt.
7. If `test.bin.gz` contains only 1 bits, increment LENGTH and GOTO 3.
8. Replace test.bin.gz with its lexicographic successor by interpreting it as a LENGTH-byte unsigned integer and incrementing it by 1.
9. GOTO 5.
test.bin.gz contains your minimal gzip encoding.
There are "stronger" compressors for popular compression libraries like zlib that outperform the "best" options available, but none of them are this exhaustive because you can surely see how the problem rapidly becomes intractable.
For the purposes of generating an efficient zip bomb, though, it doesn't really matter what the exact contents of the output file are. If your goal is simply to get the best compression ratio, you could enumerate all possible files with that algorithm (up to the bounds established by compressing all zeroes to reach your target decompressed size, which makes a good starting point) and then just check for a decompressed length that meets or exceeds the target size.
I think I'll do that. I'll leave it running for a couple days and see if I can generate a neat zip bomb that beats compressing a stream of zeroes. I'm expecting the answer is "no, the search space is far too large."
I'm an idiot, of course the search space is too large. It outgrows what I can brute force by the heat death of the universe by the time it gets to 16 bytes, even if the "test" is a no-op.
I would need to selectively generate grammatically valid zstd streams for this to be tractable at all.
It’s a zip bomb, so does the creator care? I just mean from a practical standpoint - overflows and crashes would be a fine result.
"But when I detect that they are either trying to inject malicious attacks, or are probing for a response" how are you detecting this? mind sharing some pseudocode?
Is there any legal exposure possible?
Like, a legitimate crawler suing you and alleging that you broke something of theirs?
Disclosure: IANAL
The CFAA[1] prohibits:
> knowingly causes the transmission of a program, information, code, or command, and as a result of such conduct, intentionally causes damage without authorization, to a protected computer;
As far as I can tell (again, IANAL) there isn't an exception if you believe said computer is actively attempting to abuse your system[2]. I'm not sure if a zip bomb would constitute intentional damage, but it is at least close enough to the line that I wouldn't feel comfortable risking it.
[1]: https://www.law.cornell.edu/uscode/text/18/1030
[2]: And of course, you might make a mistake and incorrectly serve this to legitimate traffic.
I don't believe the client counts as a protected computer because they initiated the connection. Also a protected computer is a very specific definition that involves banking and/or commerce and/or the government.
Part B of the definition of "protected computer" says:
> which is used in or affecting interstate or foreign commerce or communication, including a computer located outside the United States that is used in a manner that affects interstate or foreign commerce or communication of the United States
Assuming the server is running in the states, I think that would apply unless the client is in the same state as the server, in which case there is probably similar state law that comes into affect. I don't see anything there that excludes a client, and that makes sense, because otherwise it wouldn't prohibit having a site that tricks people into downloading malware.
The word "accessed" is used multiple times throughout the law. A client accesses a server. A server does not access a client. It responds to a client.
Also, the protected computer has to be involved in commerce. Unless they are accessing the website with the zip bomb using a computer that also is uses for interstate or foreign commerce, it won't qualify.
> The word "accessed" is used multiple times throughout the law.
So what? It isn't in the section I quoted above. I could be wrong, but my reading is that transmitting information that can cause damage with the intent of causing damage is a violation, regardless of if you "access" another system.
> Also, the protected computer has to be involved in commerce
Or communication.
Now, from an ethics standpoint, I don't think there is anything wrong with returning a zipbomb to malicious bots. But I'm not confident enough that doing so is legal that I would risk doing so.
There is IMO no legal use case for an external computer system to initiate a connection with my system without prior legal agreement. It all happens on good will and therefore can be terminated at any time.
There is IMO no legal use case for an external computer system to initiate a connection with my system without prior legal agreement. It all happens on good will.
Just crossed my mind that perhaps lots of bot traffic is coming from botnets of unaware victims who downloaded a shitty game or similar, orchestrated by a malicious C&C server somewhere else. (There was a post about this type of malware recently.) Now, if you crash the victims machine, it’s complicated at least ethically, if not legally.
Though anyone can sue anyone, not doing X is the simplest thing that might avoid being sued for doing X.
But if it matters pay your lawyer and if it doesn’t matter, it doesn’t matter.
Please, just as a conversational piece, walk me through the potentials you might think there are ?
I'll play the side of the defender and you can play the "bot"/bot deployer.
Well creating a bot is not per se illegal, so assuming the maliciousness-detector on the server isn’t perfect, it could serve the zip bomb to a legitimate bot. And I don’t think it’s crazy that serving zip bombs with the stated intent to sabotage the client would be illegal. But I’m not a lawyer, of course.
Disclosure, I'm not a lawyer either. This is all hypothetical high level discussion here.
> it could serve the zip bomb to a legitimate bot.
Can you define the difference between a legitimate bot, and a non legitimate bot for me ?
The OP didn't mention it, but if we can assume they have SOME form of robots.txt (safe assumtion given their history), would those bots who ignored the robots be considered legitimate/non-legitimate ?
Almost final question, and I know we're not lawyers here, but is there any precedent in case law or anywhere, which defines a 'bad bot' in the eyes of the law ?
Final final question, as a bot, do you believe you have a right or a privilege to scrape a website ?
Anyone can sue anyone for anything and the side with the most money is most likely to prevail.
Mantrapping is a fairly good analogy, and that's very illegal. If the person reading your gas meter gets caught in your mantrap, you're going to prison. You're probably going to prison if somebody burglarizing you gets caught in your mantrap.
https://en.wikipedia.org/wiki/Mantrap_(snare)
Of course their computers will live, but if you accidentally take down your own ISP or maybe some third-party service that you use for something, I'd think they would sue you.
>User-agent: *
>Disallow: /zipbomb.html
Legitimate crawlers would skip it this way only scum ignores robots.txt
I’m not sure that’s enough, robots.txt isn’t really legally binding so if the zip bomb somehow would be illegal, guarding it behind a robots.txt rule probably wouldn’t make it fine.
> robots.txt isn’t really legally binding
Neither is the HTTP specification. Nothing is stopping you from running a Gopher server on TCP port 80, should you get into trouble if it happens to crash a particular crawler?
Making a HTTP request on a random server is like uttering a sentence to a random person in a city: some can be helpful, some may tell you to piss off and some might shank you. If you don't like the latter, then maybe don't go around screaming nonsense loudly to strangers in an unmarked area.
Who, running a crawler which violates robots.txt, is going to prosecute/sue the server owner?
The server owner can make an easy case to the jury that it is a booby trap to defend against trespassers.
Has any similar case been tried? I'd think that a judge learning the intent of robots.txt and disallow rules is fairly likely to be sympathetic. Seems like it could go either way, I mean. (Jury is probably more a crap-shoot.)
> Before I tell you how to create a zip bomb, I do have to warn you that you can potentially crash and destroy your own device
Surely, the device does crash but it isn’t destroyed?
> For the most part, when they do, I never hear from them again. Why? Well, that's because they crash right after ingesting the file.
I would have figured the process/server would restart, and restart with your specific URL since that was the last one not completed.
What makes the bots avoid this site in the future? Are they really smart enough to hard-code a rule to check for crashes and avoid those sites in the future?
Seems like an exponential backoff rule would do the job: I'm sure crashes happen for all sorts of reasons, some of which are bugs in the bot, even on non-adversarial input.
I also had the idea of zip bomb to confuse badly behaved scrapers (and I have mentioned it before to some other people, although I did not implemented it). However, maybe instead of 0x00, you might use a different byte value.
I had other ideas too, but I don't know how well some of them will work (they might depend on what bots they are).
The different byte values likely won't compress as well as all 0s unless they are a repeating pattern of blocks.
An alternative might be to use Brotli which has a static dictionary. Maybe that can be used to achieve a high compression ratio.
I meant that all of the byte values would be the same (so they would still be repeating), but a different value than zero. However, Brotli could be another idea if the client supports it.
I am ignorant as to how most bots work. Could you have a second line of defense for bots that avoid this bomb: Dynamically generate a file from /dev/random and trickle stream it to them, or would they just keep spawning parallel requests? They would never finish streaming it, and presumably give up at some point. The idea would be to make it more difficult for them to detect it was never going to be valid content.
You want to consider the ratio of your resource consumption to their resource consumption. If you trickle bytes from /dev/random, you are holding open a TCP connection with some minimal overhead, and that's about what they are doing too. Let's assume they are bright enough to use any of the many modern languages or frameworks that can easily handle 10K/100K connections or more on a modern system. They aren't all that bright but certainly some are. You're basically consuming your resources to their resources 1:1. That's not a winning scenario for you.
The gzip bomb means you serve 10MB but they try to consume vast quantities of RAM on their end and likely crash. Much better ratio.
Also might open up a new DoS vector on entropy consumed by /dev/random so it can be worse than 1:1.
Entropy doesn't really get "consumed" on modern systems. You can read terabytes from /dev/random without running out of anything.
That's clear. It all comes down to their behavior. Will they sit there waiting to finish this download, or just start sending other requests in parallel until you dos yourself? My hope is they would flag the site as low-value and go looking elsewhere, on another site.
This article on Endlessh also shows how to implement a resource-light http tarpit: https://nullprogram.com/blog/2019/03/22/
This would work, but at times bots pretend not to be bots, so you occasionally do this to a real user
For HTTP/1.1 you could send a "chunked" response. Chunked responses are intended to allow the server to start sending dynamically generated content immediately instead of waiting for the generation process to finish before sending. You could just continue to send chunks until the client gives up or crashes.
[0]: https://en.wikipedia.org/wiki/Chunked_transfer_encoding
This will waste your bandwidth and resources too
The idea is to trickle it very slowly, like keeping a cat occupied with a ball of fluff in the corner.
Cats also have timeouts set for balls of fluff. They usually get bored at some point and either go away or attack you :)
If the bot is connecting over IPv4, you only have a couple thousand connections before your server starts needing to mess with shared sockets and other annoying connectivity tricks.
I don't think it's a terrible problem to solve these days, especially if you use one of the tarpitting implementations that use nftables/iptables/eBPF, but if you have one of those annoying Chinese bot farms with thousands of IP addresses hitting your server in turn (Huawei likes to do this), you may need to think twice before deploying this solution.
Yes but you still need to keep a connection open to them. This is a sort of reverse SlowLoris attack, though.
Yeah but in the mean time it's tying up a connection on your webserver.
Practically all standard libraries have timeouts set for such requests, unless you are explicitly offering streams which they would skip.
Do you mind sharing your specs of your digital ocean droplet? I'm trying to setup one with less cost.
The blog runs on a $6 digital ocean droplet. It's 1GB RAM and 25GB storage. There is a link at the end of the article on how it handles typical HN traffic. Currently at 5% CPU.
See also (2017) HN, https://news.ycombinator.com/item?id=14707674
There's a lot of creative ideas out there for banning and/or harassing bots. There's tarpits, infinite labyrinths, proof of work || regular challenges, honeypots etc.
Most of the bots I've come across are fairly dumb however, and those are pretty easy to detect & block. I usually use CrowdSec (https://www.crowdsec.net/), and with it you also get to ban the IPs that misbehave on all the other servers that use it before they come to yours. I've also tried turnstile for web pages (https://www.cloudflare.com/application-services/products/tur...) and it seems to work, though I imagine most such products would, as again most bots tend to be fairly dumb.
I'd personally hesitate to do something like serving a zip bomb since it would probably cost the bot farm(s) less than it would cost me, and just banning the IP I feel would serve me better than trying to play with it, especially if I know it's misbehaving.
Edit: Of course, the author could state that the satisfaction of seeing an IP 'go quiet' for a bit is priceless - no arguing against that
Wouldn't it be cheaper to use Cloudflare than task a human to obsessively watch webserver logs on a box lacking proper filtering?
It's also cheaper to search Google Images for "Eiffel tower" than booking a flight to Paris and going there, but a lot of people enjoy doing the latter.
Many people would be better off sticking with the former than realizing what Paris actually is and being disappointed.
https://en.wikipedia.org/wiki/Paris_syndrome
I think it's a good idea, but it must be coupled with robots.txt.
I was looking through my logs yesterday.
Bad bots don't even read robots.txt.
AI scraper bots don't respect robots.txt
I think that's the point, you'd use robots.txt to direct Googlebot/Bingbot/etc away from countermeasures that could potentially mess up your SEO. If other bots ignore the signpost clearly saying not to enter the tarpit, that's their own stupid fault.
The ones that survive do
it'd be cool to have a proof of work protocol baked into http. like, a header that browsers understood
Zip libraries aren’t bomb proof yet? Seems fairly easy to detect and ignore, no?
This topic comes up from time to time and I'm surprised no one yet mentioned the usual fearmongering rhetoric of zip bombs being potentially illegal.
I'm not a lawyer, but I'm yet to see a real life court case of a bot owner suing a company or an individual for responding to his malicious request with a zip bomb. The usual spiel goes like this: responding to his malicious request with a malicious response makes you a cybercriminal and allows him (the real cybercriminal) to sue you. Again, except of cheap talk I've never heard of a single court case like this. But I can easily imagine them trying to blackmail someone with such cheap threats.
I cannot imagine a big company like Microsoft or Apple using zip bombs, but I fail to see why zip bombs would be considered bad in any way. Anyone with an experience of dealing with malicious bots knows the frustration and the amount of time and money they steal from businesses or individuals.
Anyone can sue anyone else for any reason.
This is what trips me up:
>On my server, I've added a middleware that checks if the current request is malicious or not.
There's a lot of trust placed in:
>if (ipIsBlackListed() || isMalicious()) {
Can someone assigned a previously blacklisted IP or someone who uses a tool to archive the website that mimics a bot be served malware? Is the middleware good enough or "good enough so far"?
Close enough to 100% of my internet traffic flows through a VPN. I have been blacklisted by various services upon connecting to a VPN or switching servers on multiple occasions.
Mildly amusing, but it seems like this is thinking that two wrongs make a right, so let us serve malware instead of using a WAF or some other existing solution to the bot problem.
The web is overrun by malicious actors without any sense of morality. Since playing by the rules is clearly not working, I'm in favor of doing anything in my power to waste their resources. I would go a step further and try to corrupt their devices so that they're unable to continue their abuse, but since that would require considerably more effort from my part, a zip bomb is a good low-effort solution.
There's no ethical ambiguity about serving garbage to malicious traffic.
They made the request. Respond accordingly.
Based on the example in the post, that thinking might need to be extended to "someone happening to be using a blocklisted IP." I don't serve up zip bombs, but I've blocklisted many abusive bots using VPN IPs over the years which have then impeded legitimate users of the same VPNs.
This is William Gibson's "black ICE" becoming real, and I love it.
https://williamgibson.fandom.com/wiki/ICE
WAF isn't the right choice for a lot of people: https://news.ycombinator.com/item?id=43793526
At least, not with the default rules. I read that discussion a few days ago and was surprised how few callouts there were that a WAF is just a part of the infrastructure - it is the rules that people are actually complaining about. I think the problem is that so many apps run on AWS and their default WAF rules have some silly content filtering. And their "security baseline" says that you have to use a WAF and include their default rules, so security teams lock down on those rules without any real thought put into whether or not they make sense for any given scenario.
Something like https://xeiaso.net/notes/2025/anubis-works/
I did actually try zip bombs at first. They didn't work due to the architecture of how Amazon's scraper works. It just made the requests get retried.
Amazon's scraper has been sending multiple requests per second to my servers for 6+ weeks, and every request has been returned 429.
Amazon's scraper doesn't back off. Meta, google, most of the others with identifiable user agents back off, Amazon doesn't.
If it's easy, sleep 30 before returning 429. Or tcpdrop the connections and don't even send a response or a tcp reset.
So first, let me prefix this by saying I generally don't accept cookies from websites I don't explicitly first allow, my reasoning being "why am I granting disk read/write access to [mostly] shady actors to allow them to track me?"
(I don't think your blog qualifies as shady … but you're not in my allowlist, either.)
So if I visit https://anubis.techaro.lol/ (from the "Anubis" link), I get an infinite anime cat girl refresh loop — which honestly isn't the worst thing ever?
But if I go to https://xeiaso.net/blog/2025/anubis/ and click "To test Anubis, click here." … that one loads just fine.
Neither xeserv.us nor techaro.lol are in my allowlist. Curious that one seems to pass. IDK.
The blog post does have that lovely graph … but I suspect I'll loop around the "no cookie" loop in it, so the infinite cat girls are somewhat expected.
I was working on an extension that would store cookies very ephemerally for the more malicious instances of this, but I think its design would work here too. (In-RAM cookie jar, burns them after, say, 30s. Persisted long enough to load the page.)
You're seeing an experiment in progress. It seems to be working, but I have yet to get enough data to know if it's ultimately successful or not.
Just FYI temporary containers (Firefox extension) seem to be the solution you're looking for. It essentially generates a new container for every tab you open (subtabs can be either new containers or in the same container). Once the tab is closed it destroys the container and deletes all browsing data (including cookies). You can still whitelist some domains to specific persistent containers.
I used cookie blockers for a long time, but always ended up having to whitelist some sites even though I didn't want their cookies because the site would misbehave without them. Now I just stopped worrying.
> Neither xeserv.us nor techaro.lol are in my allowlist. Curious that one seems to pass. IDK.
Is your browser passing a referrer?
Did you also try Transfer-Encoding: chunked and things like HTTP smuggling to serve different content to web browser instances than to scrapers?
Truly one my favorite thought-terminating proverbs.
"Hurting people is wrong, so you should not defend yourself when attacked."
"Imprisoning people is wrong, so we should not imprison thieves."
Also the modern telling of Robin Hood seems to be pretty generally celebrated.
Two wrongs may not make a right, but often enough a smaller wrong is the best recourse we have to avert a greater wrong.
The spirit of the proverb is referring to wrongs which are unrelated to one another, especially when using one to excuse another.
> "Hurting people is wrong, so you should not defend yourself when attacked."
This is exactly what Californian educators told kids who were being bullied in the 90's.
> a smaller wrong is the best recourse we have to avert a greater wrong
The logic of terrorists and war criminals everywhere.
I admire your deontological zealotry. That said, I think there is an implied virtuous aspect of "internet vigilantism" that feels ignored (i.e. disabling a malicious bot means it does not visit other sites) While I do not absolve anyone from taking full responsibility for their actions, I have a suspicion that terrorists do a bit more than just avert a greater wrong--otherwise, please sign me up!
And also how fuctioning governments work: https://en.m.wikipedia.org/wiki/Monopoly_on_violence
Do you really want to live in a society were all use of punishment to discourage bad behaviour in others? That is a game theoretical disaster...
And sometimes one man's terrorist is another's freedom fighter.... (Not to defend terrorism, but it's just not that simple)
Defense and Offense are not the same.
Crime and Justice are not the same.
If you cannot figure that out, you ARE a major part of the problem.
Keep thinking until you figure it out for good.