AV-Test GmbH did a thorough test of Microsoft Security Essentials, with almost 3200 viruses, Trojans and worms. All files were detected by the AV, even those ones that aren’t yet detected and cleaned by other paid AV software. They also tested it for false positives, where an AV points out legitimate software as a virus, and even then MSE passed the test with flying colors. None of the clean files were marked as malicious by it.
