Bitdefender, Norton Top Mac Antivirus Ratings

If the old "Macs don't get viruses" chestnut was ever true, it's certainly not anymore. While Mac operating systems don't face quite the same never-ending deluge of malware as their Windows counterparts, one of the best Mac antivirus software programs can thwart a lot of nasty code that even careful Mac owners will come across now and then.

According to a new study, Bitdefender and Norton Symantec protect Mac systems the best while consuming the least system resources, while the free ClamXav software doesn't get the job done at all.

The results come courtesy of Madgeburg, Germany-based security firm AV-TEST. The company periodically evaluates how well various antivirus programs protect operating systems, including current versions of Windows, Mac OS X and Android. (For our takes on antivirus software for the other two platforms, check out our pages on the best antivirus software and the best Android antivirus apps.)

This is the first time the company has tested Mac antivirus programs since September 2014, and the results are much better this time around.

AV-TEST evaluated 10 different Mac antivirus programs, both free and paid: Avast! Free Antivirus, Avira Free Antivirus, Bitdefender Antivirus for Mac, ClamXav, Intego VirusBarrier, Kaspersky Internet Security, McAfee Internet Security, Norton Internet Security, Sophos Anti-Virus and Webroot SecureAnywhere. Rather than giving each program a comprehensive rating, it measured protection and usability separately.

Bitdefender and Norton performed the best of the bunch, scoring 100-percent in both on-demand and on-access protection. Maik Morgenstern, chief technology officer at AV-TEST, explained to Tom's Guide that "on-demand" protection refers to user-initiated scans (e.g., to root out malware already on your system), while "on-access" protection scans files as a user opens them (e.g., to prevent malicious files that you download accidentally). The former is generally more resource-intensive and comprehensive, while the latter is more likely to keep you safe from attacks as they happen.

In addition to their sterling detection rates, Bitdefender and Norton also consumed very few system resources. The former took a 1-percent toll on overall computer performance, while the latter did not effect any kind of measurable change.

For the most part, the rest of the programs performed well, too. Avast!, Avira and Kaspersky all scored 100-percent in on-demand protection, and in the mid-to-high 90s for on-access protection. McAfee, Intego, and Sophos all scored in the 90s for on-demand protection as well, although Sophos dipped into the high 80s — generally not considered safe enough — for on-access.

Webroot scored in the high 80s for both forms of protection, which is not catastrophic, but not ideal. Of the programs tested, only ClamXav totally bombed them, scoring only 39.62 percent in on-demand and 54.65 percent in on-access protection. This is arguably better than nothing, especially for a free program, but Avira and Avast provided excellent protection for free.

In terms of performance, McAfee, Webroot and Kaspersky all affected performance within single percentage points. Avast!'s system load climbed to 10 percent, ClamXav's to 13 percent, Avira's to 18 percent, Sophos' to 33 percent and Intego's to a system-crushing 48 percent.

The bottom line from the AV-TEST findings is this: You should defend your Mac, and Bitdefender and Norton seem most capable of doing so right now. ClamXav, you can give a miss. If you want a free program, both Avast! and Avira perform while putting some stress on overall system performance.

Marshall Honorof is a senior writer for Tom's Guide. Contact him at Follow him @marshallhonorof. Follow us @tomsguide, on Facebook and on Google+.

Marshall Honorof

Marshall Honorof is a senior editor for Tom's Guide, overseeing the site's coverage of gaming hardware and software. He comes from a science writing background, having studied paleomammalogy, biological anthropology, and the history of science and technology. After hours, you can find him practicing taekwondo or doing deep dives on classic sci-fi.