McAfee Antivirus Plus (formerly VirusScan plus; $40 for a one-year, single-PC license, as of 11/19/09) does well with traditional, signature-based malware detection, but it delivered a large number of false positives and fumbled on essentials like proactive protection and scan speed. Overall, it ranked tenth out of the 11 products in our roundup of stand-alone antivirus programs.

When put up against AV-Test.org's huge cache of spyware, Trojans, and other malware, McAfee's program successfully identified an impressive 99.9 percent of samples, which earned it a second-place rank in that category behind G-Data. Then again, most of the programs we tested handled basic signature detection well.

However, the apps we tested differed greatly in their ability to proactively protect against new malware that didn't yet have a full signature. Here, McAfee's offering disappointed. In heuristic tests that use two-week-old signature files and newer malware, the program detected only 56.8 percent of AV-Test.org's samples. Six other programs did a better job.

Antivirus Plus mitigates that lackluster heuristic detection with its ability to check unknown files against online servers, which means that the latest available signatures will always be used. And the company proved quick in providing those signatures, usually within two hours of any given outbreak. Only Symantec was as nimble in its outbreak response.

But online crooks devote a great deal of effort to evading signature detection, and Antivirus Plus lacks any ability to identify malware based solely on behavior. Behavioral analysis provides a strong extra layer of proactive protection; Antivirus Plus, however, wasn't able to block any malware in behavioral tests.

The program also fared poorly in disinfection tests. Every other app we evaluated was able to detect and disable all of the test malware infections, and while McAfee disabled what it found, it failed to detect one of the ten.

The bad news continued with scan speed. The app's data throughput for automatic scans that occur when you save or copy a file, for instance, was a pokey 7.06MB per second. Only Trend Micro Antivirus + Antispyware was slower. And McAfee made the most mistakes when it came to putting up false alerts about harmless files. Its 15 incorrect results was more than twice as many as the next worst showing (Kaspersky had 6).

McAfee does offer some nice extras with its app. For one thing, subscribers get all future program updates for free, with no need to pay extra for new software versions. Also, the company doesn't offer any antivirus programs without a firewall, so you'll get one with Antivirus Plus (we didn't test the firewall for this roundup, however).

Antivirus Plus is also relatively easy to use, and its warning pop-ups display plenty of information when it finds a threat. But some good features and a decent user interface can't outweigh a poor job at many critical protection tasks.