I have a linux VPS and I received a complaint that my server was scanning on port 22 some other network. How do I find out if it was compromised or not?
3 Answers
I answered a question earlier today that has recommendations in this area:
Linux backdoors I should be wary of
If you suspect that it may have been one of your users and your default shell is bash, you can grep through the .bash_history
. For example:
grep nmap /home/*/.bash_history
It's notable that your users can modify the history unless you've introduced methods to make it more difficult.
Well, if you WERE scanning.... what is the doubt?
-
I'm not scanning dude. That is the problem lol– Jene HackmanMar 9, 2010 at 22:15
-
How you know? Take a measurement from outside (firewall, router in front, wahtever).– TomTomMar 10, 2010 at 6:13
You have to think outside the box. As in, you can't really trust what's inside the box.
For instance, get your provider to monitor outgoing traffic. Traffic you can't explain => assume the server has been compromised.
Get an image of the hard drive (extracted using trusted binaries) and run forensics.