Yes. At this point, fail2ban has become almost a shibboleth for people following security checklists as opposed to reasoning about a coherent threat model. This is a perennial topic on HN, and almost always devolves to some appeal to grooming logs, because of all the authentication errors fail2ban is presumably preventing.
Don't use fail2ban. (Don't use passwords, either!)
I am one of the people to whom you refer. I read about fail2ban in a "Linux Server Bible" e-book around 2010 and have used it on all of my servers since, even though I am careful with my keys and use password-less login.
Does fail2ban have authorization to write firewall rules? That's a high-impact vector of attack, should fail2ban have a vulnerability. Also, does fail2ban store credentials that provide that authorization?
While I agree fail2ban is a wrong tool to prevent password brute force - better authentication mechanisms should be used instead - it has its uses. For example, it can be used to automatically ban (or alert about) dumb http scanners like gobuster. I am not saying, a determined attacker cannot bypass it, but if it saves me some hassle and raises the bar for them, why should not I do it?
More general, some attacker actions, especially during recon, rely on making many attempts to connect, fetch an URL, resolve FQDN, etc., these could be detected and automatically responded to, making attacker’s job harder and providing extra visibility to defenders.
You shouldn’t use it because fail2ban itself can (and has been) attacked. It doesn’t make the attackers job meaningfully harder but does add complexity to your systems, that complexity is weakness.
Yeah, that’s command injection in mailutils I mentioned, not in fail2ban itself. Did you see how it’s supposed to be exploited? Did you see a real-life exploitation?
While it’s a nice trick, it’s simply not relevant. And the vulnerability before that seems to be 10 years old. I’d say it’s a decent track record.
You have that exactly backwards: if someone is hitting you with a password bruteforce from a single IP address (which is the only threat that fail2ban mitigates) then it is assuredly nothing personal at all.
A personal insult, if you are ever unfortunate enough to receive one, will be much more stealthy and neither fail2ban nor any other magical rock will protect you against it.
If anything, you're doing them a (miniscule) favor by keeping them from wasting more resources on failed login attempts. If you really hated them, you'd set up a honeypot.
More fun: setup a fail2ban actionban script that instead of banning the IP, shapes the traffic coming from it to have abysmal bandwidth so requests/responses takes really long time, so they'll have to timeout instead of getting failures.
As that gaps of inequality of our winner takes all societies ever widen, anyone just trying to do something for themselves and not for global scale SV company is just meaninglessly role playing.
Not really. Only that reading logs by human or even grepping "manually" is super inefficient where you can make a script that will for instance send you a notification when someone actually logs into your VPS.
In world where "login attempts" are basically all day reality reading logs is meaningless. In 2023 no one should be reading logs you should have alerts on events. In 1995 or something if someone was trying to brute-force your user password that was security event to look at and block IP. In 2023 someone brute-forcing is not an event, it is either wrong configuration like not using ssh authentication or not using tools that filter logs automatically and make alerts when something is actually going on.
Don't use fail2ban. (Don't use passwords, either!)
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