Boo,
By coincidence, Consumer Reports did a review of the “free” anti-virus packages in the July 2015 issue.
Ratings as follows:
Top of the list went to: Avira (Free Antivirus 2015)
Next was AVD (AntiVirus Free 2015)
And then…..Avast (Free Antivirus 2015)
Last on the list was Microsoft Windows 8.1 with Defender
MARK