Detecting Rootkits on a Linux machine
Rootkits are a piece (or pieces) of software that someone can be used once a system is compromised to a) regain access to a system and b) remove traces of a compromise and c) many times hide itself. There are some tools for linux based systems that can be run to detect traces of rootkits and probably the best known is a tool called chkrootkit. I’ve know of it for what seems like years now and it can run a relatively quick test for traces of a wide range of KNOWN linux rootkits.
There is a good tutorial on how to install and use it here what’s probably the best to point out is that you should not install and then just run it occasionally, it should be put either on read-only media, or removable media so that an attacker could not discover it’s presence and alter it to ignore the attackers rootkit. (Or you could keep a local copy just to give them something else to do and do your REAL scanning from a read-only/removable… )
I did find a referral to another rootkit detectorrkhunter which I haven’t yet tested, but looks promising… a more direct link is here.
Happy rootkit hunting?