[SlowToady]

http://articles.techrepublic.com.com/5100-6350-5034641.html

Let me pull out a few key parts.

Aside from Klez, other major viruses affecting Linux/UNIX platforms include the Lion.worm, the OSF.8759 virus, Slapper, Scalper, Linux.Svat, and the BoxPoison virus—just to mention a few.

An Austrian student named Alexander Bartolich has even written a guide to writing the ELF virus for Linux. Bartolich does not claim to be a Linux virus pioneer and says that he has only more efficiently documented and formatted in a nicer way the virus, worm, and Trojan vulnerabilities for Linux that have already been documented elsewhere. With such revealing documents posted on the Web, the proliferation of UNIX-based viruses is only going to increase, especially since the use of Linux in the server room is increasing. However, systems administrators may want to get a jump on Linux viruses by reading the guide themselves so they can better understand Linux vulnerabilities.

Emphasis mine.

Other good parts, too, but I'll leave that you guys to read.