Microsofts free antivirus solution for all Windows users may be good in terms of usability - in particular, its impact on system performance - but when it comes to actual malware protection, it came almost dead last amongst its free and paid competitors in tests conducted during the first quarter of 2011 by German testing firm AV-Test. In fact, an almost identical observation can be made for AV-Tests previous tests conducted in the fourth quarter of 2010 on Windows Vista. Fortunately for Microsoft, despite these results the product did manage a pass and a certification from AV-Test.
The results were spotted by PCWorld, who are quick to point out that despite MSEs poor showing, it performed very well on samples of widespread malware and those on AV-Tests reference set that were discovered in the past two or three months. The problem is with 0-day samples and the resident scanners ability to stop malware from running or after it ran. In particular, MSE caught only 50% of 0-day malware attacks in March, and only stopped 45% of malware from running. The industry averages are 84% and 62%, respectively. There were a total of 22 antivirus solutions tested.
Curiously, the only other free antivirus that was tested in that list was Avast!, which fared better than MSE but not by much. It was ranked 14th. In comparison to MSEs two weak spots, Avast! caught 80% of 0-day malware in March, but blocked only 41% of malware from executing. Other free antivirus vendors, such as AVG and Avira, submitted their paid "premium" suites for testing instead of their free solutions. Both ranked higher than Avast! and MSE, coming at sixth for AVG and tenth for Avira.
The winner in terms of protection ratings was BitDefender Internet Security Suite 2011. BullGuard Internet Security 10.0, F-Secure Internet Security 2011, Kaspersky Internet Security 2011, and Norton Internet Security 2011 tied for second.
The full report may be found here.