Linus is not malware-proof. It is[/is] better than Windows in that regard, though. I would agree with Darkseeker's list, plus Microsoft Security Essentials, much as I hate to say it.
Personally, I use a firewall appliance running a Linux-based firewall OS and running CLAMAV, but even then, bad stuff can be brought in by my clients (read: family), and for the Windows units, MSE worked great for rooting out the nasties.
Oh, and Norton's is teh crap...