How to defend your website with ZIP bombs (2017)

https://blog.haschek.at/2017/how-to-defend-your-website-with-zip-bombs.html

by BonoboIO • 3 years ago

122 74 3 years ago

blog.haschek.at

zubairq• 3 years ago

Nice, I didn’t even know that ZIP bombs existed! I have seen some huge spam traffic on servers I run in the past so this will be a good tool for me to use. Thanks

cyberax• 3 years ago

TIL today: ZIP bombs are still a thing, 40 years after the first BBS.

theshrike79• 3 years ago

Similar things were popular in the DC++ age too.

Some servers required you to have X gigabytes of stuff in your shares, so you just had a zip bomb in your share with the correct size.

It reported the size as 10GB to the server, but actually it took a few kilobytes on disk.

iforgotpassword2• 3 years ago

I've done this without compression but just sending infinite data. On some days I've sent a TB to a single IP address... Might be an idea to combine this. I'd assume the resulting gzip file here contains a repeating pattern that you can generate on the fly?

tuyiown• 3 years ago

A zip bomb is way more effective as it will be transferred very quickly and saturate attacker storage as fast as possible, with a good probability to make the system inoperable (login into a machine with with 0 storage left can be challenging).

Retr0id• 3 years ago

Yes, it would be trivial to make an "endless" gzip stream.

lifthrasiir5• 3 years ago

And if you need an explicit binary, it is very easy to make one. Prepare a large enough file filled with the same byte (or generate them on the fly), let gzip to compress it, then observe where the zero byte start to repeat. Cut everything after that point and repeat the zero byte from there on. In my system:

    $ head -c 10000000 /dev/zero | gzip -c -9 | hexdump
    0000000 8b1f 0008 530a 659e 0302 c1ec 0101 0000
    0000010 8000 fe90 eeaf 0a08 0000 0000 0000 0000
    0000020 0000 0000 0000 0000 0000 0000 0000 0000
    *
    0002010 0000 0000 0000 db80 0383 0012 0000 4100
    0002020 5fff 23b7 0150 0000 0000 0000 0000 0000
    0002030 0000 0000 0000 0000 0000 0000 0000 0000
    *
    00025f0 0000 0000 0000 0000 0000 0000 0000 e000
    0002600 cb26 3ba5 803e 9896 0000
    0002609

So you can keep the first 0x18 bytes and repeat zero bytes after that, preferably very slowly. (The middle bit is an arbitrary block boundary, while the last bit is CRC-32 and the uncompressed size which the client will never see.) I have also used `-c` option to avoid the original file name in the result, which precedes the compressed data.

inglor_cz• 3 years ago

Was your hosting OK with that? ZIP bombs are light on the "data transferred" front, a TB is pretty massive.

iforgotpassword2• 3 years ago

I've got a limit of 50TB which I never came even close to. I'm still with them, but the script got lost at some point.

pixl973• 3 years ago

The other thing to do here is tarpitting/slow feeding data keeping the bot busy for a long time. Not sure if modern bots are better at timing out than in the past.

joshspankit2• 3 years ago

Back in the day if you had a faster modem and typed faster than the other person’s modem could receive, you could kick them offline.

The more things change, the more they stay the same?

nicbou• 3 years ago

Had it had a marked effect on the bots? Dropping *.php calls helped a lot.

reaperman• 3 years ago

Is it legal to purposefully distribute a malicious payload as a booby trap?

ksjskskskkk• 3 years ago

never link to it and add to robots.txt

digital castle doctrine or whatever.

artiscode• 3 years ago

Is it really malicious though? 10 gigs of zeros doesn’t seem that malicious to me. Microcontrollers often have a few megabytes of RAM if not less, does that make a few megabyte photo malicious?

Edit: spelling. I’m old school and used to typing on my computer. It’s getting repaired and all I’ve got is my phone. /rant

Avamander3• 3 years ago

It's a joke answer at best, plus if someone would go complain, their actions for discovering the booby trap were illegal anyways.

esdf2• 3 years ago

I wouldn’t try it in Japan https://github.com/hamukazu/lets-get-arrested

JohnFen2• 3 years ago

I don't think that a zip bomb counts as "malicious". I can't think of a law (in the US) that would prohibit doing this sort of thing.

ehPReth• 3 years ago

https://42.zip served just that (after the 42.zip named on https://en.wikipedia.org/wiki/Zip_bomb) until some ****hole reported it to Google/etc for.... phishing? Kinda sad, lol.

One of the arguments I've seen is: 'what if your antivirus scans it' to which I think: if your antivirus blows up on a zip bomb in 2024, you need a new antivirus that isn't total garbage?

geek_at• 3 years ago

This could be the result of a google indexing error. Strangeley enough my blog (the one linked in this hn post) itself was de-listed from google justa few weeks ago.

The Blog is a static HTML page with no external dependencies and I didn't even update it in the time google thought there was phishing somewhere.

The Webmastertools showed the error but didn't link to any specific site (it even said null).

So i sent it in to re-evaluate and it was put back on google (without changing anything on the static files themselves). Very strange stuff

koito17• 3 years ago

If I recall correctly, HTTP clients do not need to care about Content-Encoding at all and can choose to just not do anything with your ZIP bomb. To really hit them, you will want to do this at the Transfer-Encoding level.

lifthrasiir5• 3 years ago

If the client wants to parse HTML and do something accordingly, it at least has to honor some popular Content-Encoding.

_xnmw• 3 years ago

In the spirit of a good offence is the best defence, etc., I wonder if there are any other ways to defend my website.

stareatgoats• 3 years ago

related: https://news.ycombinator.com/item?id=14707674 (July 6, 2017 — 183 comments)

hannob4• 3 years ago

People have been coming up with ideas like that regularly. I'm not a fan.

The title says that you can "defend" your webpage, but it is not clear how it "defends" against anything. The only thing you possibly achieve is that every now and then, someone with an automated scanner (which may be an attacker, or may be a security researcher or service) will see his tool crash or consume large amounts of resources.

You're spending time trying to annoy attackers that you should probably just ignore. If you really worry that someone running some automated scanner against your webpage causes you any harm, you probably should spend your time with something different than building zip bombs, and instead fix the security problems you have.

Avamander3• 3 years ago

Slowing down and resisting unauthorised scanners does sound like one more layer of defence to me.

bayindirh2• 3 years ago

you probably should spend your time with something different than building zip bombs, and instead fix the security problems you have.

Why not both? You can both create a well configured server to reduce its attack surface and add a booby-trap or two for really adamant scanners which hit very specific endpoints on your site.

I don't have to welcome every scanner with open arms. Maybe I'm doing some research, PoC||GTFO style, and your scanner found my research. It's not my problem.

Freak_NL• 3 years ago

PoC||GTFO style

waihtis2• 3 years ago

Perhaps used to be true, however I believe active countermeasures will grow in importance in the near future. We are on the cusp of seeing a lot more sophisticated class of automated attacks (once the malicious cyber actors get a grasp on how to use LLM's in their favour) and active disruption of these capabilities will be important, not just building more shields around yourself. Before that, we need to fast-track the normalization of using active countermeasures as most are in the same camp as you are.

dns_snek2• 3 years ago

Please elaborate, how are LLMs going to provide a "more sophisticated" class of automated attacks, and how are toy countermeasures like ZIP bombs going to defend against these "sophisticated" attacks?

I could believe you if you said that ZIP bombs are perhaps mildly effective against script kiddies using ChatGPT to generate a naive, simplistic automated scanners that are susceptible to being "zip bombed". The other way around? Not so much.

These zip bombs are trivial to defend against as an attacker, e.g. by inspecting the payload while you're decompressing it to see if it matches some expected output (an <html> tag, for example) or by aborting after the decompressed size exceeds some limit (10 MB is way more HTML than you'd typically expect, for example).

noobermin• 3 years ago

It really is only in the world of IT security is this attitude so pervasive, where you constantly blame victims. While defense is a great offense it can't hurt to be an annoyance to bad actors.

el_oni• 3 years ago

unless it paints a target on your back

hannob4• 3 years ago

Can you tell me where in my words you read that I blamed victims? I think you're reading something into it that isn't there.

raverbashing• 3 years ago

For real

I definitely blame the "oh we should do nothing" approach to the current security situation

Yes, if you want to be the lame duck and get scanned leisurely by the bad actors and diligently serving 404s etc be my guest.

Then we wonder why email became useless outside of the big providers, and every site needs to behind a CDN, etc

foul2• 3 years ago

You're spending time trying to annoy attackers that you should probably just ignore.

s/ignore/block at firewall-level/

To me this article is of relevance nonetheless because It inspires me for messing with AI trainers by crafting an html page ZIP bomb full of ZIP-bomb-like embedded attachments (stylesheets, images, etc).

hannob4• 3 years ago

No, ignore.

WAFs that "block" "attacks" that ultimately should just cause a 404 error are part of the same mindset: That you think you "have to do something" about an attack that you should probably just ignore. They're also part of the mindset that security should mean adding more complexity, which is the opposite of what you should do.

berkes2• 3 years ago

I use fail2ban for this. I know what my servers run (and it's never PHP, Python microsoft/AD sharepoint etc, because I don't have services in these languages or systems) so I simply fail2ban everything that matches these broad items.

Access "wp-admin"? Ban. Try "cron.php" ban. Looking for "phpmyadmin"? ban.

It works reasonably well. These bots can switch to other IPs, or try again after the jailtime is lifted (20 mins in my case). But instead of a bot attempting thousands of endpoints, I get only one attempt.

I initially configured this on a backend, that for reasons, had to handle every URL in the (Ruby, so heavy and slow) application layer: a bot trying common endpoints for popular CMSes and services, would put severe load on this application. Fail2ban was already there, blocking SSH, FTP, SMTP and whatnot, so I configured it to also handle these HTTP endpoints.

ivancho3• 3 years ago

No one is really worried, and no time is wasted when the outcome is occasional fun. There's no security holes to fix, there's just a bunch gnats poking at your server and you shoo them away, that's all.

hannob4• 3 years ago

If your goal is "fun" then I guess that's fine. But don't pitch it as "defending" your website.

JohnFen2• 3 years ago

The only thing you possibly achieve is that every now and then, someone with an automated scanner (which may be an attacker, or may be a security researcher or service) will see his tool crash or consume large amounts of resources.

True. But it's also a low-cost, low-effort thing. It may not change the world, but putting a small hiccup in someone's operation can bring a small bit of joy.

cosmin800• 3 years ago

Not sure it works for the scanners, sure it crashes the browsers, but I would guess most scanners use libcurl which has a callback function for saving data and would give up on loading the resource if over 2MiB let's say.

o-o-• 3 years ago

Another method that stuck with me: in the early days of bitcoin someone built an "ssh paywall" – i.e. you would pay to enable ssh remote authentication for a minute or two.

In essence a hacker would have to pay before attempting to hack the ssh endpoint. Of course the admin would have to pay too but the money would end up on his/her wallet.

Quite ingenious if you ask me.

joshspankit2• 3 years ago

Stuff like this is going to be wild when digital transaction fees for tiny amounts are basically free and transactions can be truly anonymous.

lifthrasiir5• 3 years ago

If the client supports Brotli, this attack can be made much more effective because the maximum compression ratio of Brotli is much higher than gzip. DEFLATE used by gzip has the maximum ratio of 1032:1 because each run can emit at most 258 bytes and need at least 2 bits, but Brotli allows zero bits per code when there is only one code possible. So Brotli's result only depends on the underlying metablock overhead, but sadly each metablock can contain at most 2^24 - 1 uncompressed bytes (because that uncompressed size is encoded per each metablock, while DEFLATE needs a separate end-of-block code). Still this translates to at least 1000000:1 ratio so it's worthwhile.

Avamander3• 3 years ago

This can also be done with nginx's gzip_static/brotli_static, somewhat easier.

One similar technique against port scanners is to send ~50% rejects and do ~50% drops in the case of closed ports. Most of them will pollute their output or slow down tremendously assuming packet loss.

justsomehnguy• 3 years ago

How to defend your website with ZIP bombs

.. or more like 'How to retaliate when you think too much of your [website] importance'.

While the ability to (maaaaybe) crash the crawler sounds nice it probably doesn't do what do you think. At best you just snapped off one head of Hydra, only more to come.

Also using PHP instead of the web-server's path actions...

13of40• 3 years ago

It reminds me of someone I read about from the early web who defended their website against email address harvesting crawlers by adding a dynamic page that threw up some random emails and links, where the links just led back to the dynamic page under a new path on the same host. The crawlers would get stuck downloading millions of fake email addresses until they eventually broke.

kxrm• 3 years ago

Guilty, I did this on my first project site back in the early 00s. It only worked for a small time before scanners got more sophisticated. It was a fun diversion but people who do this quickly adapt.

Log_out_• 3 years ago

What if the returned content is just chat gpt generated add hoc nonsense in the amount nonsense heuristics-1 ?

InfamousRece• 3 years ago

I used wpoison back then: https://www.gsp.com/support/virtual/web/cgi/lib/wpoison/

mcqueenjordan3• 3 years ago

This reminds me of the chat bot tool that was deployed to reply to scam emails and waste maximal time of the scammers by seeming like a vulnerable, gullible target. The chat bot would drag out the interaction slowly, wasting as much time as possible for the scammer, all the while posing as a real human.

There are a lot of comments here decrying this as a method to defend your website, but in some senses it's a very smart tactical weapon, especially if deployed widely. There's an often quoted phrase in making secure password hashes that you're not making it impossible to crack, only prohibitively expensive to do so such that the benefits don't outweigh the costs. The same principle applies here -- if the good guys collectively make scanning a very expensive endeavor, the juice is no longer worth the squeeze for the bad guys. Just blocking an IP is cheap for them. Make them bleed a little.

mcqueenjordan3• 3 years ago

Another possible tactic is to trickle your packets back slowly, say trickle 1 TCP packet back to them per second. Sure, they probably have client-side timeouts, but again, if everyone did this, wouldn't it be a pain to scan for vulns? Every endpoint you hit would last the duration of your timeout.

pixl973• 3 years ago

Do modern bots deal with TARPITTING better? This was something that was pretty common years ago when dealing with bots.

naich• 3 years ago

I tried the example with FF on Ubuntu, and it had no effect whatsoever. It didn't even use up any memory. Are browsers protecting against this now?

_V_• 3 years ago

I have something similar - except I don't send them ZIP bombs, but I engage in something akin to a Slowloris attack. I keep the connection open and send random bytes with random delays in between.

To my surprise, I got few "champions" who spend >12h on a socket trying to get data that lead nowhere. And since there is ultimately a limit on number of sockets on a system, you can effectively DDoS that attacker.

mglz• 3 years ago

This script obviously is not - as we say in Austria - the yellow of the egg, [...]

I think my pig is whistling!

How to defend your website with ZIP bombs (2017)

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