Interesting informations and links about viruses on Linux. Stuff that is good to know:
articles
[http://librenix.com/?inode=21 The short life and hard times of a Linux virus]
[http://www.users.qwest.net/~eballen1/virefs.html Papers and books relating to Unix Computer Viruses]
prototypes
[http://www.kernelthread.com/publications/security/vunix.html Viruses on Unix] some very simple code examples
[http://www.kernelthread.com/publications/security/src/jb.c Jingle Bell] simple ELF virus source code
[http://math-www.uni-paderborn.de/~axel/bliss/ Bliss] smarter ELF virus, never opensourced
[http://www.1010.co.uk/promiscuOS.html promiscu OS] interesting concept of a self reproducing distro