Microsoft's free Security Essentials package rates well at removing malware and running light, but what about dealing with brand-new, unidentified bad stuff? Turns out Security Essentials is still the best at figuring out what's bad — while also avoiding annoying false positives.
In a follow-up to their previous performance tests, long-running testing site AV-Comparatives.org loaded up antivirus and malware prevention suites with definition updates from February 2010, but slipped them malware and other bad stuff that had been detected and defined since then. This was to test the heuristic and analytic powers of these security suites — in other words, to see if the software could figure out up-to-the-minute malware, even if their providers haven't catalogued them yet in an update, or if the update hasn't hit your computer yet.
The straight-up performance of 20 security suites is shown in this graph, excerpted from AV-Compartives' full report (click for a larger view).
That chart only shows detection of the known bad stuff. For balance, AV-Comparatives also checked how often each software provided false positives — warning of potential viruses and the like on benign software. As a site with AutoHotKey-based apps that generates a lot of incorrect security warnings, we're sensitive to this measure of quality.
So while Microsoft Security Essentials wasn't the absolute winner in finding new malware without a definition available, it was the best performing among those apps that had "Very few false alarms" — perfect for software that's free and light on resources.
On that level, F-Secure also detected smartly with few annoyances, as did BitDefender. You can read the full report at the direct PDF link below, or see AV-Comparatives's backlog of tests at their main test results list. Thanks to Charles for sending in the link!
Independent Tests of Anti-Virus Software [AV-Comparatives]
Proactive/Retrospective Test (Direct PDF link)