Hi, recently (ironically, right after sharing some of my posts here on Lemmy) I had a higher (than usual, not high in general) number of “attacks” to my website (I am talking about dumb bots, vulnerability scanners and similar stuff). While all of these are not really critical for my site (which is static and minimal), I decided to take some time and implement some generic measures using (mostly) Crowdsec (fail2ban alternative?) and I made a post about that to help someone who might be in a similar situation.
The whole thing is basic, in the sense that is just a way to reduce noise and filter out the simplest attacks, which is what I argue most of people hosting websites should be mostly concerned with.
Fail2ban + key-based SSH + self-hosted WAF if you can spin up another machine == 80% of your Web hosting problems gone
Good read.
I would just like to add some additional information that favors changing your SSH port to something other than the default. When crawlers are going around the internet looking for vulnerable SSH servers, they’re more than likely going to have an IP range and specifically look for port 22.
Now can they go through and scan your IP and all of its ports to look for the SSH service? Yes. But you will statistically have less interactions with bad actors this way since they might specifically be looking for port 22.
As a side note, don’t be cute and pick port 221 or 2222 or 22022 or whatever that’s got “22” in it.
I know that sounds silly but the slightly less stupid bots are written by people who understand people do things like that and account for them, and thus port 2222 isn’t actually better than 22, or whatever.
imho - never expose that shit anyways, and VPN into your local network first. Only thing I ever expose to the internet is 80/443.
At the very least, if you’re going to expose an SSH session to the internet, set up some sort of port-knocking. It’s security by obscurity, sure - but it will keep all but the most ardent intruders out.
Thanks! I did mention this briefly, although I belong to the school that “since I am anyway banning IPs that fail authentication a few times, it’s not worth changing the port”. I think that it’s a valid thing especially if you ingest logs somewhere, but if you do don’t choose 2222! I have added a link to shodan in the post, which shows that almost everybody who changes port, changes to 2222!
Yeah, I just left my SSH port as 22 since I only use key-based authentication so there’s really no security risk. Plus, it’s funny going through the logs and looking at all the login attempts.
Yep I agree. Especially looking at all the usernames that are tried. I do the same and the only risk come from SSH vulnerabilities. Since nobody would burn a 0-day for SSH (priceless) on my server, unattended upgrades solve this problem too for the most part.
There is one neat trick: don’t expose SSH.
There is still not a reason anyone has been able to give for 99% of self-hosters to expose SSH.
If you need to access your machine via ssh while on the go. Wireguard to your local network, use SSH. Done. Unless you are running an always-up public facing site, the amount of times you have to access your machine that can’t wait until after work is very low anyway.
Bots will scan all ports. That is just how it works. Less than 22, but you will still get spammed. Why force your computer to go through the fail2ban loop and take up resources when it is simply not needed at all and you can block it on another machine?
Comfort is the main reason, I suppose. If I mess up Wireguard config, even to debug the tunnel I need to go to the KVM console. It also means that if I go to a different place and I have to SSH into the box I can’t plug my Yubikey and SSH from there. It’s a rare occurrence, but still…
Ultimately I do understand both point of view. The thing is, SSH bots pose no threats after the bare minimum hardening for SSH has been done. The resource consumption is negligible, so it has no real impact.
To me the tradeoff is slight inconvenience vs slightly bigger attack surface (in case of CVEs). Ultimately everyone can decide which compromise is acceptable for them, but I would say that the choice is not really a big one.
Some people also swear by other measures, like changing the SSH port to something else. Most people end up using 2222 to easily remember. This is borderline useless, as you can see for yourself.
While being useless against a sophisticated attacker, there hasn’t been any bot activity in my sshd logs since changing my ssh port to a different one.
Yeah, what I mean is that it’s useless using ports like 2222, that’s like the unofficial SSH port! Bots are generally harmless (once you move to key auth), and you get functional the same result with the automatic IP ban on failed auth, minus the bother to change client configurations to your custom port. Anyway, if someone does want cleaner logs, changing port works :)
I recall hearing that openssh has something like fail2ban built-in now. I forget the name of the feature.
AFAIK I know that SSH has MaxAuthTries and LoginGraceTime, but all it does is terminating the SSH session (I.e. slow down at most), it won’t block the IP via firewall or configuration.
Not sure if there is a recent feature that does the same.
It’s this (excuse formatting): https://www.openssh.com/releasenotes.html
sshd(8) will now penalise client addresses that, for various reasons, do not successfully complete authentication. This feature is controlled by a new sshd_config(5) PerSourcePenalties option and is on by default.
sshd(8) will now identify situations where the session did not authenticate as expected. These conditions include when the client repeatedly attempted authentication unsucessfully (possibly indicating an attack against one or more accounts, e.g. password guessing), or when client behaviour caused sshd to crash (possibly indicating attempts to exploit bugs in sshd).
When such a condition is observed, sshd will record a penalty of some duration (e.g. 30 seconds) against the client’s address. If this time is above a minimum configurable threshold, then all connections from the client address will be refused (along with any others in the same PerSourceNetBlockSize CIDR range) until the penalty expire.
Repeated offenses by the same client address will accrue greater penalties, up to a configurable maximum. Address ranges may be fully exempted from penalties, e.g. to guarantee access from a set of trusted management addresses, using the new sshd_config(5) PerSourcePenaltyExemptList option.
Genuine question from someone with a single page static site - why is Cloudflare a useless suggestion?
Fair question. What I meant is that suggesting that would have made the whole post 10 lines long and not worth doing. So I avoided such suggestions that completely change the threat model.
It’s not useless to avoid a good security posture (although you might have concerns of a monopoly gatekeeping the internet, TLS traffic inspection privacy concerns etc.), on the contrary makes everything I have written about here redundant (+ provide more, like DDoS protection) as you are outsourcing the security controls.
