Firewalls and virus scaners?

[Courtenay W]

Hey,
Relatively new to linux/ubuntu (about 9 months now), currently running
9.04.
This is the first I've heard suggested to get a firewall and virus
scanner. I realize there is always some risk of hack/malware, but my
impression was that linux is seriously less at risk than, say, Windows.
Am I wrong? Should I be running regular virus scans, as I did on
Windows?
Thanks,
Courtenay W
Calgary AB