Bitdefender, F-Secure, Kaspersky Rated Top Anti-Virus Suites

Here's some good news for PC users: If Windows is your operating system of choice, just about any of the best antivirus software will protect you from almost everything malefactors can throw your way, according to the latest results from the AV-TEST security institute.

AV-TEST, a security firm based in Madgeburg, Germany, subjected 28 security suites to a battery of exhaustive tests to determine which could best protect user PCs. Included in the running were major providers like Bitdefender, free services like AVG and the built-in Microsoft Windows Defender. (The lab also tests the best Mac antivirus software and the best Android antivirus apps.)

The first step in testing the suites was to expose them to 400 strains of brand-new, or "zero day," malware. The programs would have no prior knowledge of these threats, meaning they would have to rely on their detection algorithms to separate dangerous software from benign system files.

The second test measured each program's efficacy in detecting and removing 60,000 known pieces of malware. Instead of simply having a program scan a machine and erase all offending files, researchers gave each program a chance to exercise all of its security protocols to detect malware, including real-time monitoring.

Finally, AV-TEST measured each program's system demands and usability. Having a virus detection program that slows your computer to a crawl, AV-TEST argued, is a virus detection program hardly worth using. Likewise, not knowing how to access most of a program's features essentially renders it useless.

The top contenders

In the first test battery, three programs received 100 percent ratings across the board: Bitdefender, F-Secure and Kaspersky Lab. Those who use G Data, Symantec, BullGuard, Trend Micro, Avast, Microworld, AVG or ESET have little to worry about, though: their ratings range between 97 and 100 for both real-world detection and the reference tests.

Windows Defender scored considerably less well in the real-world trial, however: It detected only 79 percent of zero day malware programs, even though it succeeded in isolating 97 percent of known threats.

Bitdefender, F-Secure and Kaspersky Lab also tested extremely well in the practical categories, coming in first, fourth and second, respectively (Symantec came in third). Results were decidedly more mixed here, though: Some lightweight programs were not very intuitive, and some system hogs were as easy-to-use as software gets.

Once again, Microsoft Windows Defender came in almost at the bottom of the list, placing 14th out of 15. On a 6-point scale, AV-TEST gave the program an abysmal 1.0 on Protection, a decent 3.8 in System Load, although it earned a perfect 6.0 in Usability.

Based on AV-TEST's results (which took six months to fully perform and analyze), Microsoft's own software is woefully inadequate for protecting Windows PCs, but almost any other program — even the best free antivirus software — should do just fine.

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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.