“For the second time in a row, Microsoft Security Essentials has failed to be certified as effective by AV-Test.org, an independent testing lab based in Germany.
The lab publishes test results every two months, and the test from November and December 2012 looked at 25 consumer antivirus security programs. Three failed certification: PC Tools Internet Security 2012, AhnLab Internet Security 8.0, and Microsoft Security Essentials 4.1.”
Source: Microsoft bombs another security test | Internet security and firewall – CNET Reviews