Personal firewalls: The 'other' antivirus software - Computerworld

Personal firewalls: The 'other' antivirus software - Computerworld: "They come under different names -- SubSeven, NetBus, Deep Throat, Back Orifice or the recent Mydoom -- but they share a common trait: They open a back door to an infected system. You wouldn't leave the back door of your home or business open to intruders, and your computer merits the same prudence.
Most commercially available antivirus products will detect known worms and Trojans containing back doors, but malicious code evolves rapidly, and new, more sophisticated threats surface daily. Worms can spread very quickly, and antivirus vendors aren't always able to develop and disseminate updates in time to prevent a major outbreak. "