On November 21 the blogosphere was abuzz when Apple updated a technical note on its Support Web site that says
Apple encourages the widespread use of multiple antivirus utilities so that virus programmers have more than one application to circumvent, thus making the whole virus writing process more difficult.
Virus software manufacturer Intego quickly jumped on the bandwagon and promoted the fact that their VirusBarrier X5 software was recommended by Apple.
Apple spokesperson Bill Evans said:
We have removed the KnowledgeBase article because it was old and inaccurate... The Mac is designed with built-in technologies that provide protection against malicious software and security threats right out of the box... However, since no system can be 100 percent immune from every threat, running antivirus software may offer additional protection.
Bottom line: if you're running any sort of Windows virtualization software (like Parallels or VMWare) you should definitely be running Windows-based firewall and anti-virus software.