Network Security Hacks

Scan for Root Kits

Use chkrootkit to determine the extent of a compromise.

If you suspect that you have a compromised system, it is a good idea to check for root kits that the intruder may have installed. In short, a root kit is a collection of programs that intruders often install after they have compromised the root account of a system. These programs will help the intruders clean up their tracks, as well as provide access back into the system. Because of this, root kits will sometimes leave processes running so that the intruder can come back easily and without the system administrator’s knowledge. This means that some of the system’s binaries (like ps, ls, and netstat) will need to be modified by the root kit in order to not give away the backdoor processes that the intruder has put in place. Unfortunately, there are so many different root kits that it would be far too time-consuming to learn the intricacies of each one and look for them manually. Scripts like chkrootkit (http://www.chkrootkit.org) will do the job for you automatically.

In addition to detecting over 50 different root kits, chkrootkit will also detect network interfaces that are in promiscuous mode, altered lastlog files, and altered wtmp files. These files contain times and dates of when users have logged on and off the system, so if they have been altered, this is evidence of an intruder. In addition, chkrootkit will perform tests in order to detect kernel module-based root kits. C programs that are called ...