The new version of the popular security software features signature-based protection against malware that can be installed when the user downloads pictures, music, and software. Symantec said that 78 percent of attacks take place at this level.

Set It and Forget It

Even though Macs are less of a target for malware, Symantec noted that the machines still can pass malicious software to others by e-mail, instant messages, or Web links. The other machines can be either PCs or Macs, so AntiVirus 11 scans for viruses and other vulnerabilities for both platforms.

AntiVirus 11 can gather updates in the background, so it can protect with what Symantec called "set it and forget" convenience. The software also has less impact on system startup and resource use, according to the company.

The newly updated interface features wizards to indicate system status, and a new Norton AntiVirus dashboard widget that shows a summary of current protection levels. For users who hate to be interrupted in the middle of a movie scene, scheduled virus scans can be moved to a less intrusive time with the "snooze button."

Antivirus Needed for Macs?

For power users, there is a command line interface via the Terminal, for adding virus scans and custom scripts as desired. But some Mac users, power or not, invariably ask whether antivirus software is needed for their platform.

Apple itself promotes Macs as being less vulnerable to viruses than PCs. On its Web site, for instance, it said that while "no computer connected to the Internet will ever be 100 percent immune from attack, Mac OS X has helped the Mac keep its clean bill of health with a superior Unix foundation and security features that go above and beyond the norm of PCs."

In a column last month for the Washington Post, computer security expert Brian Krebs said he is often asked by Mac users whether they should use antivirus software. He wrote that "there are very few examples of malicious software in the wild built for Mac users," but said that every user should be aware of risks when using the Internet, such as in downloading software from sites whose credibility is unknown.

Other experts have noted that many Macs are used in multiplatform environments, and could spread viruses to PCs if the Macs themselves do not have adequate protection.

The new version of Norton AntiVirus for the Mac costs $49.95 and includes one year of updates.