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.
Around the same time, or maybe even earlier, some random company sent me a junk fax every Friday. Multiple polite voicemails to their office number were ignored, so I made a 100-page PDF where every page was a large black rectangle, and used one of the new-fangled email-to-fax gateways to send it to them. Within the hour, I got an irate call. The faxes stopped.
Circa 1997 a coworker lamented that he had signed up for some email list, and attempts to unsubscribe weren’t working (more of a manual thing, IIRC). I made the suggestion to set up a cronjob to run hourly, to send an email request to be unsubscribed. It would source a text file containing the request to be unsubscribed. And with each iteration, it would duplicate the text from the file, effectively a geometric progression. The list owner responded about a week or so later, rather urgently requesting that my coworker cut it out, saying that he would remove him from the list. Apparently the list owner had been away on vacation the entire time.
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 always liked the RP DNS record (https://www.rfc-editor.org/rfc/rfc1183) but no one seems to know about it or use it any more. The only reason my servers don't have one now is because route53 doesn't support it.
I had a lazy fix for a down detection on my RPi server at home, it was pinging a domain I owned and if it couldn't hit that assumed it wasn't connected to a network/rebooted itself. I let the domain lapse and this RPi kept going down around 5 minutes... thought it was a power fault, then I remembered about that CRON job.
You’d be surprised to know, that in a majority of the cases of NT installations in that era, providing services, there were very, very few admins around to even notice what was going on. Running services like this on an NT box was done ‘in order to not have to have an admin’, in so many thousands of cases, it cannot be underestimated.
Disclaimer: I put a lot of servers on the Internet in the 90’s/early 2000’s. It was industry-wide standard practice: ‘use NT so you don’t need an admin’.
I never found this out, but there was some feature where NT would try to negotiate an encrypted connection to communicate and that’s the port it was connecting on. It’s a long time ago. It’s possible the box had been pwned, and that was command/control for a botnet or something. Lots of internet-facing windows boxes were at the time because MS security was absolutely horrendous at this time.
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.
I wonder if I could create a 500TB html file with proper headers on a squashfs, an endless <div><div><div>... with no closing tags, and if I could instruct the server to not report file size before download.
Why use squashfs when you can do the same OP did and serve a compressed version, so that the client is overwhelmed by both the uncompression and the DOM depth:
Yes, servers can respond without specifying the size by using chunked encoding. And you can do the rest with a custom web server that just handles request by returning "<div>" in a loop. I have no idea if browsers are vulnerable to such a thing.
I am not sure how that could’ve worked. Unless the real /dev tree was exposed to your webserver’s chroot environment, this would’ve given nothing special except “file not found”.
The whole point of chroot for a webserver was to shield clients from accessing special files like that!
I guess it depends on the server's implementation. but, since you need some logic to decide when to serve the html bomb anyway, I don't see why you would prefer this solution. Just use whatever script you're using to detect the bots to serve the bomb.
"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.
So I actually do this (use compression to filter out bots) for my one million checkboxes Datastar demo[1]. It relies heavily on streaming the whole user view on every interaction. With brotli over SSE you can easily hit 200:1 compression ratios[2]. The problem is a malicious actor could request the stream uncompressed. As brotli is supported by 98% of browsers I don't push data to clients that don't support brotli compression. I've also found a lot of scrapers and bots don't support it so it works quite well.
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
Last time I checked, the tab keeps loading, freezes, and the process that's assigned to rendering the tab gets killed when it eats too much RAM. Might cause a "this tab is slowing down your browser" popup or general browser slowness, but nothing too catastrophic.
How bad the tab process dying is, depends per browser. If your browser does site isolation well, it'll only crash that one website and you'll barely notice. If that process is shared between other tabs, you might lose state there. Chrome should be fine, Firefox might not be depending on your settings and how many tabs you have open, with Safari it kind of depends on how the tabs were opened and how the browser is configured. Safari doesn't support zstd though, so brotli bombs are the best you can do with that.
> 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.
I once worked for a US state government agency and my coworker was the main admin of our WordPress based portal and it was crazy how much work it was to keep working.
I never hosted WP, but as soon as you have a HTTP server expose to the internet you will get request to /wp-login and such. It as become a good way to find bots also. If I see an IP requesting anything from a popular CMS, hop it goes in the iptables holes
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)
Weird that text browsers just ignore all the attributes that hide elements. I get that they don't care about styling, but even a plain hidden attribute or aria-hidden are ignored.
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.
> 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.
This is the main reason I haven't installed zip bombs on my website already -- on the off chance I'd make someone angry and end up having to fend off a DDoS.
Currently I have some URL patterns to which I'll return 418 with no content, just to save network / processing time (since if a real user encounters a 404 legitimately, I want it to have a nice webpage for them to look at).
Should probably figure out how to wire that into fail2ban or something, but not a priority at the moment.
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.
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.
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.
Kinda wonder if a "content labyrinth" could be used to influence the ideas / attitudes of bots -- fill it with content pro/anti Communism, or Capitalism, or whatever your thing is, hope it tips the resulting LLM towards your ideas.
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.
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 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.
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.
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.
There is a similar thing for ssh servers, called endlessh (https://github.com/skeeto/endlessh). In the ssh protocol the client must wait for the server to send back a banner when it first connects, but there is no limit for the size of it ! So this program will send an infinite banner very ... very slowly; and make the crawler/script kiddie script hang out indefinitely or just crash.
Hilarious because the author, and the OP author, are literally zipping `/dev/null`. While they realize that it "doesn't take disk space nor ram", I feel like the coin didn't drop for them.
Other than that, why serve gzip anyway? I would not set the Content-Length Header and throttle the connection and set the MIME type to something random, hell just octet-stream, and redirect to '/dev/random'.
I don't get the 'zip bomb' concept, all you are doing is compressing zeros. Why not compress '/dev/random'? You'll get a much larger file, and if the bot receives it, it'll have a lot more CPU cycles to churn.
Even the OP article states that after creating the '10GB.gzip' that 'The resulting file is 10MB in this case.'.
Is it because it sounds big?
Here is how you don't waste time with 'zip bombs':
$ time dd if=/dev/zero bs=1 count=10M | gzip -9 > 10M.gzip
10485760+0 records in
10485760+0 records out
10485760 bytes (10 MB, 10 MiB) copied, 9.46271 s, 1.1 MB/s
real 0m9.467s
user 0m2.417s
sys 0m14.887s
$ ls -sh 10M.gzip
12K 10M.gzip
$ time dd if=/dev/random bs=1 count=10M | gzip -9 > 10M.gzip
10485760+0 records in
10485760+0 records out
10485760 bytes (10 MB, 10 MiB) copied, 12.5784 s, 834 kB/s
real 0m12.584s
user 0m3.190s
sys 0m18.021s
$ ls -sh 10M.gzip
11M 10M.gzip
The whole point is for it to cost less (ie, smaller size) for the sender and cost more (ie, larger size) for the receiver.
The compression ratio is the whole point... if you can send something small for next to no $$ which causes the receiver to crash due to RAM, storage, compute, etc constraints, you win.
No, it's not about sending large files over the wire, it's about saturating the RAM of the script that reads the content. If the script is naive enough, a zip bomb will do. Example on my machine, such a snippet will cause the OS to close the python process:
>>> from requests import get
>>> r = get("https://acme.tld/trap/")
>>> r.text
The server doesn't do much (serving a relatively small number of bytes) while the client basically crashes.
As an aside, there are a lot of people out there standing up massive microservice implementations¹ for relatively small sites/apps, which need to have this part printed, wrapped around a brick, and lobbed at their heads:
> A well-optimized, lightweight setup beats expensive infrastructure. With proper caching, a $6/month server can withstand tens of thousands of hits — no need for Kubernetes.
----
[1] Though doing this in order to play/learn/practise is, of course, understandable.
It's probably watching for connections to files listed in robots.txt that should not be crawled, etc. Once a client tries to do that thing (which it was told not to do), then it gets tagged malicious and fed the zip file.
Long story short, I use memcached to track ips, user agent, and the use of POST method. The requests per minute, request payload, and past behavior will make isMalicious() return true.
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.
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."
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).
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.
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
}
}'
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.
As I don't use PHP in my server, but get a lot of requests for various PHP related stuff, I added a rule to serve a Linux kernel encrypted with a "passphrase" derived from /dev/urandom as a reply for these requests. A zip bomb might be a worse reply ...
For all those "eagerly" fishing for content AI bots I ponder if I should set up a Markov chain to generate semi-legible text in the style of the classic https://en.wikipedia.org/wiki/Mark_V._Shaney ...
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.
> 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.
Just put a "by connecting to this service, you agree to and authorize…" at the front of the zipbomb.
(I'm half-joking, half-crying. It's how everything else works, basically. Why would it not work here? You could even go as far as explicitly calling it a "zipbomb test delivery service". It's not your fault those bots have no understanding what they're connecting to…)
So the trick is to disguise it as an accident. Have the zip bomb look like a real HTML file at the beginning, then have zeroes after that, like it got corrupted.
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.
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.
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.
A user has to manually unpack a zip bomb, though. They have to open the file and see "uncompressed size: 999999999999999999999999999" and still try to uncompress it, at which point it's their fault when it fills up their drive and fails. So I don't think there's any ethical dilemma there.
> 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.
Compressing a sequence of any single character should give almost identical results length-wise (perhaps not exactly identical, but the difference will be vanishingly small).
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.
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.
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.
It is surprising that it works (I haven't tried it). `Content-Length` had one goal - to ensure data integrity by comparing the response size with this header value. I expect http client to deal with this out of the box, whether gzip or not. Is it not the case? If yes, that changes everything, a lot of servers need priority updates.
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.
"On my server, I've added a middleware that checks if the current request is malicious or not"
How accurate is that middleware? Obviously there are false negatives as you supplement with other heuristics. What about false positives? Just collateral damage?
I guess it goes without saying, that the first thing should be to follow security best practices. Patch vulnerabilities fast etc., before doing things like that. Then maybe his first website wouldn't have compromised either.
I like a similar trick, sending very large files hosted on external servers to malicious visitors using proxies. Usually those proxies charge by bandwidth, so it increases their costs.
"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?
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.
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
Rust born processes are memory-safe in terms of avoiding corruption of their heaps & stacks by C-like problems like rogue pointers and use-after-free, but they are still subject to OOM conditions, or running out of other storage, so can easily be killed by a zip-bomb if not coded in an appropriately defensive manner.
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.
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.
As a former boss used to say: "Unlimited is a bad idea."
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.
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Around the same time, or maybe even earlier, some random company sent me a junk fax every Friday. Multiple polite voicemails to their office number were ignored, so I made a 100-page PDF where every page was a large black rectangle, and used one of the new-fangled email-to-fax gateways to send it to them. Within the hour, I got an irate call. The faxes stopped.
Circa 1997 a coworker lamented that he had signed up for some email list, and attempts to unsubscribe weren’t working (more of a manual thing, IIRC). I made the suggestion to set up a cronjob to run hourly, to send an email request to be unsubscribed. It would source a text file containing the request to be unsubscribed. And with each iteration, it would duplicate the text from the file, effectively a geometric progression. The list owner responded about a week or so later, rather urgently requesting that my coworker cut it out, saying that he would remove him from the list. Apparently the list owner had been away on vacation the entire time.
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?
Back then things like postmaster@theirdomain and webmaster@theirdomain were read by actual people. Also the whois command often worked.
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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 always liked the RP DNS record (https://www.rfc-editor.org/rfc/rfc1183) but no one seems to know about it or use it any more. The only reason my servers don't have one now is because route53 doesn't support it.
tech-c / abuse addresses were commonly available on whois.
tangent
I had a lazy fix for a down detection on my RPi server at home, it was pinging a domain I owned and if it couldn't hit that assumed it wasn't connected to a network/rebooted itself. I let the domain lapse and this RPi kept going down around 5 minutes... thought it was a power fault, then I remembered about that CRON job.
That's why everyone else is lazy and just ping google.com
You’d be surprised to know, that in a majority of the cases of NT installations in that era, providing services, there were very, very few admins around to even notice what was going on. Running services like this on an NT box was done ‘in order to not have to have an admin’, in so many thousands of cases, it cannot be underestimated.
Disclaimer: I put a lot of servers on the Internet in the 90’s/early 2000’s. It was industry-wide standard practice: ‘use NT so you don’t need an admin’.
What was it about NT that made an admin unnecessary? Just marketing?
Didn't get why that WinNT box was connecting to your box. Due to some misconfigured Windows update procedure?
I never found this out, but there was some feature where NT would try to negotiate an encrypted connection to communicate and that’s the port it was connecting on. It’s a long time ago. It’s possible the box had been pwned, and that was command/control for a botnet or something. Lots of internet-facing windows boxes were at the time because MS security was absolutely horrendous at this time.
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.
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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 wonder if I could create a 500TB html file with proper headers on a squashfs, an endless <div><div><div>... with no closing tags, and if I could instruct the server to not report file size before download.
Any ideeas?
Why use squashfs when you can do the same OP did and serve a compressed version, so that the client is overwhelmed by both the uncompression and the DOM depth:
yes "<div>"|dd bs=1M count=10240 iflag=fullblock|gzip | pv > zipdiv.gz
Resulting file is about 15 mib long and uncompresses into a 10 gib monstrosity containing 1789569706 unclosed nested divs
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Yes, servers can respond without specifying the size by using chunked encoding. And you can do the rest with a custom web server that just handles request by returning "<div>" in a loop. I have no idea if browsers are vulnerable to such a thing.
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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.
I hope you weren’t paying for bandwidth by the KiB.
Nah, back then we paid for bandwidth by the kb.
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Maybe it's time for a /dev/zipbomb device.
ln -s /dev/urandom /dev/zipbomb && echo 'Boom!'
Ok, not a real zip bomb, for that we would need a kernel module.
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Wait, you set up a symlink?
I am not sure how that could’ve worked. Unless the real /dev tree was exposed to your webserver’s chroot environment, this would’ve given nothing special except “file not found”.
The whole point of chroot for a webserver was to shield clients from accessing special files like that!
You yourself explain how it could've worked: Plenty of webservers are or were not chroot'ed.
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Could server-side includes be used for a html bomb?
Write an ordinary static html page and fill a <p> with infinite random data using <!--#include file="/dev/random"-->.
or would that crash the server?
I guess it depends on the server's implementation. but, since you need some logic to decide when to serve the html bomb anyway, I don't see why you would prefer this solution. Just use whatever script you're using to detect the bots to serve the bomb.
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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)"
I remember reading about that some years ago. It involved Windows NT.
https://www.google.com/search?q=windows+nt+bug+affects+ship
Bad bot
we discovered back when IE3 came out that you could crash windows by leaving off a table closing tag.
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These days, almost all browsers accept zstd and brotli, so these bombs can be even more effective today! [This](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.
So I actually do this (use compression to filter out bots) for my one million checkboxes Datastar demo[1]. It relies heavily on streaming the whole user view on every interaction. With brotli over SSE you can easily hit 200:1 compression ratios[2]. The problem is a malicious actor could request the stream uncompressed. As brotli is supported by 98% of browsers I don't push data to clients that don't support brotli compression. I've also found a lot of scrapers and bots don't support it so it works quite well.
[1] checkboxes demo https://checkboxes.andersmurphy.com
[2] article on brotli SSE https://andersmurphy.com/2025/04/15/why-you-should-use-brotl...
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
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But the bot likely only automatically unpacks the outer layer. So nesting doesn't help with bot deterrence.
Wouldnt that defeat the attack though as you arent serving the large content anymore
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How will my browser react on receiving such bombs? I’d rather not to test it myself…
Last time I checked, the tab keeps loading, freezes, and the process that's assigned to rendering the tab gets killed when it eats too much RAM. Might cause a "this tab is slowing down your browser" popup or general browser slowness, but nothing too catastrophic.
How bad the tab process dying is, depends per browser. If your browser does site isolation well, it'll only crash that one website and you'll barely notice. If that process is shared between other tabs, you might lose state there. Chrome should be fine, Firefox might not be depending on your settings and how many tabs you have open, with Safari it kind of depends on how the tabs were opened and how the browser is configured. Safari doesn't support zstd though, so brotli bombs are the best you can do with that.
gzip it's everywhere and it will mess with every crawler.
> 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.
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Never use that junk if you value your sanity, I think you mean.
I once worked for a US state government agency and my coworker was the main admin of our WordPress based portal and it was crazy how much work it was to keep working.
Ditto to self-hosting wordpress works fine with standard hosting practices and not installing a bazillion random plugins.
I never hosted WP, but as soon as you have a HTTP server expose to the internet you will get request to /wp-login and such. It as become a good way to find bots also. If I see an IP requesting anything from a popular CMS, hop it goes in the iptables holes
Hey, I check /wp-admin sometimes when I see a website and it has a certain feel to it
I do the same. Great way to filter our security scanners.
Wordpress is indeed a nice backdoor, it even has CMS functionality built in.
>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.
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We use to just call those honeypot fields. Works like a charm.
Oh that is great.
apart from blind users, who are also now completely unable to use their screenreaders with your site
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Check this out if you want to stop this behavior...
https://github.com/skeeto/endlessh
> 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.
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.
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I think they are suggesting the range of IPs to block is too high?
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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.
Weird that text browsers just ignore all the attributes that hide elements. I get that they don't care about styling, but even a plain hidden attribute or aria-hidden are ignored.
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.
> 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.
This is the main reason I haven't installed zip bombs on my website already -- on the off chance I'd make someone angry and end up having to fend off a DDoS.
Currently I have some URL patterns to which I'll return 418 with no content, just to save network / processing time (since if a real user encounters a 404 legitimately, I want it to have a nice webpage for them to look at).
Should probably figure out how to wire that into fail2ban or something, but not a priority at the moment.
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%.
Same, using ipsets, and a systemd {service,timer} for updating the lists.
fail2ban automates that and is in package managers
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.
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is that endpoint detection and response?
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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.
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Wouldn't this just waste your own bandwidth/resources?
Kinda wonder if a "content labyrinth" could be used to influence the ideas / attitudes of bots -- fill it with content pro/anti Communism, or Capitalism, or whatever your thing is, hope it tips the resulting LLM towards your ideas.
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.
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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.
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 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.
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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.
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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.
There is a similar thing for ssh servers, called endlessh (https://github.com/skeeto/endlessh). In the ssh protocol the client must wait for the server to send back a banner when it first connects, but there is no limit for the size of it ! So this program will send an infinite banner very ... very slowly; and make the crawler/script kiddie script hang out indefinitely or just crash.
Attacked Over Tor [2017]
https://www.hackerfactor.com/blog/index.php?/archives/762-At...
The same, for Caddy: https://www.dustri.org/b/serving-a-gzip-bomb-with-caddy.html
10T is probably overkill though.
Hilarious because the author, and the OP author, are literally zipping `/dev/null`. While they realize that it "doesn't take disk space nor ram", I feel like the coin didn't drop for them.
Think about it:
Other than that, why serve gzip anyway? I would not set the Content-Length Header and throttle the connection and set the MIME type to something random, hell just octet-stream, and redirect to '/dev/random'.
I don't get the 'zip bomb' concept, all you are doing is compressing zeros. Why not compress '/dev/random'? You'll get a much larger file, and if the bot receives it, it'll have a lot more CPU cycles to churn.
Even the OP article states that after creating the '10GB.gzip' that 'The resulting file is 10MB in this case.'.
Is it because it sounds big?
Here is how you don't waste time with 'zip bombs':
The whole point is for it to cost less (ie, smaller size) for the sender and cost more (ie, larger size) for the receiver.
The compression ratio is the whole point... if you can send something small for next to no $$ which causes the receiver to crash due to RAM, storage, compute, etc constraints, you win.
No, it's not about sending large files over the wire, it's about saturating the RAM of the script that reads the content. If the script is naive enough, a zip bomb will do. Example on my machine, such a snippet will cause the OS to close the python process:
The server doesn't do much (serving a relatively small number of bytes) while the client basically crashes.
As an aside, there are a lot of people out there standing up massive microservice implementations¹ for relatively small sites/apps, which need to have this part printed, wrapped around a brick, and lobbed at their heads:
> A well-optimized, lightweight setup beats expensive infrastructure. With proper caching, a $6/month server can withstand tens of thousands of hits — no need for Kubernetes.
----
[1] Though doing this in order to play/learn/practise is, of course, understandable.
IsMalicious() doing some real heavy lifting in that pseudo code. Would love to see a bit more under THAT hood.
It's probably watching for connections to files listed in robots.txt that should not be crawled, etc. Once a client tries to do that thing (which it was told not to do), then it gets tagged malicious and fed the zip file.
Long story short, I use memcached to track ips, user agent, and the use of POST method. The requests per minute, request payload, and past behavior will make isMalicious() return true.
I know ive been on THAT list before. Heaven forbid i dont have chrome or keep it up to date, shame on me!
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?
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Ha ha, that compressor is some evil genius.
Brings to mind this 30+ year old IOCCC entry for compressing C code by storing the code in the file names.
https://www.ioccc.org/1993/lmfjyh/index.html
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.
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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."
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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.
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).
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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
Do must unzip programs work recursively by default?
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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"
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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.
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There's around a 64KB block size limit for a block of compressed data. That sets a max compression ratio.
gzip isn't optimal for this case. It divides the file into blocks and each one has a header. Apparently that's about 1 byte per 1000.
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
check out the lists in this repo
https://github.com/danielmiessler/SecLists/blob/master/Disco...
I combined a few of the most interesting lists from here into one and never miss an attack now
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:
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.
Check out Modsecurity WAF and CoreRuleSet.
As I don't use PHP in my server, but get a lot of requests for various PHP related stuff, I added a rule to serve a Linux kernel encrypted with a "passphrase" derived from /dev/urandom as a reply for these requests. A zip bomb might be a worse reply ...
For all those "eagerly" fishing for content AI bots I ponder if I should set up a Markov chain to generate semi-legible text in the style of the classic https://en.wikipedia.org/wiki/Mark_V._Shaney ...
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.
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.
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Just put a "by connecting to this service, you agree to and authorize…" at the front of the zipbomb.
(I'm half-joking, half-crying. It's how everything else works, basically. Why would it not work here? You could even go as far as explicitly calling it a "zipbomb test delivery service". It's not your fault those bots have no understanding what they're connecting to…)
So the trick is to disguise it as an accident. Have the zip bomb look like a real HTML file at the beginning, then have zeroes after that, like it got corrupted.
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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.
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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 ethically it might be a good thing to shut down their infected computer, instead of keeping it running.
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.
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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.
Anyone can sue anyone for anything and the side with the most money is most likely to prevail.
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.
>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.
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> 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?
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.
Yes.
A user has to manually unpack a zip bomb, though. They have to open the file and see "uncompressed size: 999999999999999999999999999" and still try to uncompress it, at which point it's their fault when it fills up their drive and fails. So I don't think there's any ethical dilemma there.
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> 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.
This post is suspiciously similar to my post from 2017 "How to defend your website with ZIP bombs"
https://blog.haschek.at/2017/how-to-defend-your-website-with...
Same concept, but I found yours more informative. Quite different overall.
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.
Compressing a sequence of any single character should give almost identical results length-wise (perhaps not exactly identical, but the difference will be vanishingly small).
For example, with gzip using default options:
Two bytes difference for a 1GiB sequence of “aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa…” (\141) compared to a sequence of \000.
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.
See also (2017) HN, https://news.ycombinator.com/item?id=14707674
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.
The worst ones treat it as a target.
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
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.
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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/
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.
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> [...] and trickle stream it to them [...]
See https://en.wikipedia.org/wiki/Slowloris_(cyber_attack)
Practically all standard libraries have timeouts set for such requests, unless you are explicitly offering streams which they would skip.
This would work, but at times bots pretend not to be bots, so you occasionally do this to a real user
It is surprising that it works (I haven't tried it). `Content-Length` had one goal - to ensure data integrity by comparing the response size with this header value. I expect http client to deal with this out of the box, whether gzip or not. Is it not the case? If yes, that changes everything, a lot of servers need priority updates.
You don't need to set a content length header, it'll take the page as finished when you close the connection
The hard part is the content of isMalicious() function. The bots can crash but they’d be quick to restart anyway.
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.
Thanks for sharing!
If anyone is interested in writing a guide to set this up with crowdsec or fail2ban I'm all ears
"On my server, I've added a middleware that checks if the current request is malicious or not"
How accurate is that middleware? Obviously there are false negatives as you supplement with other heuristics. What about false positives? Just collateral damage?
I thought he maintains his own list of offenders
The code shows both the 'middleware' and the custom list can put you in the naughty box
Can someone explain why mods change post titles? What value does it provide in their mind?
I guess it goes without saying, that the first thing should be to follow security best practices. Patch vulnerabilities fast etc., before doing things like that. Then maybe his first website wouldn't have compromised either.
I can't imagine using anything other than a stream interface when dealing with web requests in a crawler.
You need that to protect against not only these types of shenanigans, but also large or slow responses.
I like a similar trick, sending very large files hosted on external servers to malicious visitors using proxies. Usually those proxies charge by bandwidth, so it increases their costs.
"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?
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
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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
If one wanted to create the ICE of cyberspace in cyberpunk, capable to destroy the device ...
Zip libraries aren’t bomb proof yet? Seems fairly easy to detect and ignore, no?
But what about the bots written in Rust? Will that get rid of them too?
Rust born processes are memory-safe in terms of avoiding corruption of their heaps & stacks by C-like problems like rogue pointers and use-after-free, but they are still subject to OOM conditions, or running out of other storage, so can easily be killed by a zip-bomb if not coded in an appropriately defensive manner.
OP: Hi guys this is how I fend off hackers! Hackers: Note taken.
it'd be cool to have a proof of work protocol baked into http. like, a header that browsers understood
Serving a zip bomb is pretty illegal. The bot will restart its process anyway, and carry on as if nothing happened.
ok but where I put this?? at the files directory???
this was a cool read.very interesting stuff.
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
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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.
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.
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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.
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