Virus? What's one of them?
For a firewall there's lokkit or ipchains (and iptables). Seriously, you don't need a virus scanner unless:
1. You're gonna be generous and scan your mail before sending it out to windows users, or
2. You're just a bit paranoid and feel safer with one.
There are only a handful of linux viruses, none of which are harmful unless you're stupid enough to run everything as root. Essentially, if you only run as a normal user you'll be fine.