Bitdefender would come in second; Kaspersky would be in third; Avira and Emisoft would come tied in fourth.The only reason I would place Avira so low is because of their false positives.
Antivirus software can also cause bad or incorrect behavior, and random or consistent crashes.The information below is anecdotal, users like you giving their personal experiences. So if you have a problem that is not listed here, please help other users by adding your experience to the list.If experience is anything to go by, adverts, be it on the page or in a pop-up, are generally the main cause of involuntary virus-downloading.Pop ups that appear when clicking on something, or anywhere on the page. An ad blocker is useful in more ways than just removing annoyance.I know some people who are in the need for something free and effective.
Gotta love incompetent husbands who trust everything the internet says, and then blame it all on the wives!I recently started using Bitdefender's free version, just to see how much resources it uses, and how reliable I find it to be (does it trigger false positives/etc. No real complaints, but it does bog my slower computer down a noticeable amount.It's okay, but by no means would I personally use it for anything more than peace of mind.If you have a virus, just reset windows and get over it.Some of the best AV software is free, and has little to no system impact. Maximum PC ran benchmarks with and without the AV running, and the results barely changed. Because most of the others are crap / crash / slow the system down and die when you get infected anyway.