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When this topic (always) comes up, somebody points out that moving the ports isn't security...but it kinda is, because if you suddenly see an uptick in logging,
by Damogran6 5y ago
When this topic (always) comes up, somebody points out that moving the ports isn't security...but it kinda is, because if you suddenly see an uptick in logging, you know someone cares enough to FIND your port, and then POINT SOMETHING AT the port, and in the meantime it reduces heat and power and disk wear.
- yellowapple 5y ago> and in the meantime it reduces heat and power and disk wear. If drive-by SSH attempts - even a large number of them - are enough to have a noticeable impact on heat/power/wear, then you should probably consider, you know, not putting hardware from 1997 on the Internet. Really doesn't take that much energy on hardware built during the current century to reject an authentication attempt and log it.
- Damogran6 5y agoCall it a feng shui thing.
- anjbe 5y ago> it reduces heat and power and disk wear. Measurably?
- JimDabell 5y agoMoving the port reduces security. Port 22 is a privileged port. Standard users can’t listen on port 22. If you move the port to 2222 or wherever, then if an attacker with local access can get sshd to crash, they can run their own sshd instead. If you left the port as the default, they wouldn’t be able to do that without chaining it with a privilege escalation attack. But because you changed the port, you disabled this security feature and it could become a privilege escalation attack.
- throwaway2048 5y agoIts pretty trivial to disable the ability of users to listen on certain ports higher than 1024 with a firewall config.
- JimDabell 5y agoIn practice, people won’t do that. Case in point: the article doesn’t mention this mitigation at all. It introduces an additional attack vector and tells you it’s safer.
- usr1106 5y agoA firewall config can block listening? What would that firewall config be? The firewall can block packets by owner uid. But I am not sure who is the owner in legitimate sshd case. Root or the user logged in? SELinux can do it, probably other LSMs, too.
- throwaway2048 5y agoyou cant block the actual port bind, but you can block any packets from reaching it, so the difference is mostly semantics
- usr1106 5y agoYes, but that port needs to remain "open" for the legitimate sshd traffic. Can you see a difference in ownership as the firewall sees it between sshd and some user daemon? Sshd drops root partially when login succeeds.
- throwaway2048 5y agothat has nothing to do with sshd's listening socket, which remains owned by root
- usr1106 5y agoSure the listening one remains owned by root. But the connected one? If you limit packets from/to e.g. 2222 to uid 0, will legitimate ssh traffic work? I don't say it won't, genuinely unsure. Haven't tried and today is a holiday. Maybe tomorrow :)
- password4321 5y agoYour point about privileged ports is valid. So maybe change to a different but still privileged port?
- usr1106 5y agoI am not sure it reduces security. You have a valid point. I adds an attack vector. However "only" if you have the attacker in your system already. Having all the log spam from failed attempts on 22 might the make the admin negligent on carefully following their logs at all. Having it pretty silent on a higher port usually will make you notice occasional scanning. At least I have noticed it and made me tighten the firewall a bit. There is no perfect security.
- beagle3 5y agoOnly if they already have local access. And the sshd is not listening on the port (if it’s on, you can’t just bind it) And they still can’t show the host certificate, so your client would tell you the certificate changed. Unless, of course, they have a local root exploit — but then port 22 is just as unsafe. I fail to see how changing a port makes anything less safe.