What's the best free antivirus program for Windows 8? It seems like Avira, avast!, AVG, and Microsoft Security Essentials are the big ones. Avira wasn't fully compatible with Windows 8, and although an update was released earlier this month to improve this compatibility, I'm not sure if it's fully-compatible yet, but It seems to be picked as the best on a few articles I read. Some people complained of upgrade pop-ups and ads though, which I would definitely not want. avast! is what I used on my old laptop (Vista), and it seemed to work fine. AVG and MSE I've read mixed reviews about.
I have free trials of Norton Internet Security and Webroot SecureAnywhere; how does your suggested free program stack up to these?
Also, should I install additional malware protection, such as Spybot - Search & Destroy?