Most of the posts here are FUD.
Linux
does have virii, the first was in 1995.
However because you do not have admin rights by default on linux (with the exception of one distribution) they have minimal effect - they cannot infect the system;
possibly the local user might get stung but that's all they can do, they can't propogate, they can't access the system.
Its nothing to do with numbers of users, market share open vs closed source, its down to basic errors in Microsoft products.
Linux was largely developed over internet, Microsoft under-estimated the demand & effect of networking.
I do have antivirus installed, mainly so I don't pass Windows malware onto Windows users.
see:
http://www.theregister.co.uk/2003/10...ndows_viruses/
"Opinion To mess up a Linux box, you need to work at it; to mess up your Windows box, you just need to work on it, writes SecurityFocus columnist Scott Granneman."