In my opinion, running any anti virus, with the current state of the Linux world, is a waste of resources. The only reason I can think of for doing so is to help protect your fellow Windows users.
I do recommend you run your firewall, iptables, properly configured. You can use either Firestarter, (Gnome), or Guarddog, (KDE), to configure it to your needs.
Insanity: Doing the same thing over and over and each time expecting a different result.
Democracy is 2 wolves and a lamb voting on the menu. Liberty is an armed lamb protesting the electoral outcome. A Republic negates the need for an armed protest.