I'm pretty careful about what I do online and what I download. A few years back, when I used the free version of AVG with Windows XP, I had a few problems with malware, etc., but nothing that couldn't be fixed. Since I upgraded to Windows 7 three years ago, I've only been using Microsoft Security Essentials without a single problem. It's always possible something foreign could be living in my computer without me knowing about it, but nothing that impedes performance. I just feel that third party security programs are more trouble than they are worth...no matter how cheap they are.