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Coping With 1 Million SSH Authentication Failures?
An anonymous reader writes "I own a small Web development studio that specializes in open source software, primarily Drupal, WordPress, and Joomla for small businesses. Our production servers, which host about 50 sites and generate ~20K hits/week, are managed by a 3rd party that I'm sure many on Slashdot would recognize. Earlier today I was researching some problems on one of our sites and found that there have been over 1 million SSH authentication failures from ~1200 IP addresses on one of our servers over the last year. I contacted the ISP, who had promised me that server security would be actively managed, and their recommendation was, 'change the SSH port!' Of course this makes sense and may help to an extent, but it still doesn't solve the problem I'm facing: how do you manage server security on a tight budget with literally no system admin (except for me and I know I'm a n00b)? User passwords are randomly generated, we use a non-standard SSH port, and do not use any unencrypted services such as FTP. Is there a server monitoring program you would recommend? Is there an ISP or Web-based service that specializes in this?"
-A INPUT -p tcp -m tcp --dport 22 -m state --state NEW -m recent --set --name SSH --rsource -j ACCEPT
-A INPUT -p tcp -m tcp --dport 22 -m recent --update --seconds 60 --hitcount 8 --rttl --name SSH --rsource -j LOG --log-prefix "SSH_brute_force "
-A INPUT -p tcp -m tcp --dport 22 -m recent --update --seconds 60 --hitcount 8 --rttl --name SSH --rsource -j DROP
Stops 'em *somewhat* dead. If you want to whitelist hosts so they are not impacted by this rule, just add;
-A INPUT -s your.ip.address -p tcp -m tcp --dport 22 -m state --state NEW -j ACCEPT
Before the throttling ruleset.
-- The unsig...
you know what I am saying?
You can't handle the truth.
Let me see if I have this right. If iptables can keep count of incoming connections within the kernel and drop incoming connections as they happen without any intervention from a userspace program, that's _not_ automatic.
But running a gigantic shell script to scrape text messages out of your system logs and then call randomly chosen commands which may or may not have any effect on the observed problem some time after it occurs, then that's "doing that stuff automatically"?
Maybe those words don't mean what one of us thinks they do.
That, and create only a single user who can log in, that takes you to the real log in prompt. That way an attacker has to guess the one user+password, and have a legitimate userid+password to gain access.
It's not foolproof, but it foils the vast majority of script attackers.
And DISABLE ROOT LOGIN!
That's a beautiful and witty analogy but to reverse it:
If he asked "How can I stop my house being burgled?" and you said, "Without a full alarm, CCTV and patrol system, don't even bother. Leave it to the professionals."
Some others might see some practical value in suggesting, "Maybe lock your door at night."
My opinion in this situation is first to take what advice you can and do something yourself as soon as possible (since any extra security is better than nothing). Next, as you suggested and when he has the resources to employ someone to do it properly, seek professional help. Simply doing nothing until he can do it properly sounds a bit dangerous.
1 million per year over 50 sites == 20,000 per year per site, or 54 per day per site. Change the passwords every few months (and use different ones for each site).
Further - 1,200 different remote hosts means what, 17 attempts per remote host per site per year. Probably randomly p0wned PCs that hit addresses at random, make a few attempts using default or ocmmon passwords, then move on.
This is really cool until you find yourself trying to log in from the same access point where somebody with a virus was attached earlier in the day. Better to just use crypto (key-based authentication only) and rate-limiting.