The context in this post is purely based on my limited knowledge, I am not comparing myself to security experts, but I am judging antivirus softwares using freely available data that I am aware of. The technical comparison among free antivirus softwares almost does not exist, because antivirus vendors normally send their premium (read: paid) versions for tests. So far, only avast did the otherwise (see AV-Comparatives ). Many vendors actually release both free and premium versions, I am not sure whether this will completely change the test results or not, but if you read the results, even the paid versions could not guarantee 100% detection. Personally, I prefer two free antivirus softwares: Panda Cloud Antivirus and avast! Free Antivirus . I really like the idea of cloud computing and simplicity of Panda Cloud, but I switched to avast because Panda Cloud required manual program upgrade (they remedied this problem in version 1.3 ). (I had used older versions of AVG and A...