Viruses (and
especially spyware) aren't that much of a problem on Linux/Unix systems. What tends to give us more grief [though still not even remotely close to the spyware/viruses on Windows] are rootkits. If you're really serious [paranoid?] about locking down your system, you might want to install a couple rootkit checking programs such as
Rootkit Hunter and
chkrootkit.
If you want antivirus software,
Clam's definitely the way to go -- it's free software/open source and there are a few graphical front-ends to it such as
KlamAV. I use it on my Linux machines not so much to protect myself from viruses, but to keep me from passing on any potentially infected files to my Windows-using friends.
Hope that helps!
