Rootkit hunters

Rootkit Hunter scans files and systems for known and unknown rootkits, backdoors, and sniffers. The package contains one shell script, a few text-based databases, and optional Perl modules. It should run on almost every Unix clone.

http://freshmeat.net/projects/rkhunter/

chkrootkit is a tool to locally check for signs of a rootkit. It contains:

chkrootkit: shell script that checks system binaries for rootkit modification.

http://www.chkrootkit.org/

http://staff.washington.edu/dittrich/talks/blackhat/blackhat/antirootkit.html

http://www.rootkit.com/index.php