One company's name springs to mind when it comes to antivirus products: Symantec. Norton AntiVirus (NAV) is the 800-pound gorilla of antivirus software, on both the Mac and the PC, and NAV 11 proves that reputation is well deserved. This version features a new, more straightforward interface, and a new Vulnerability Protection feature that scans files and images as you download them to ensure they aren't packing viruses or malware. While it's true that Macs are relatively free of viruses, NAV also scans for Windows viruses, of which there are plenty, which means your Mac won't accidentally pass along dangerous files to your Windows-using friends.