Hmmm ... not the type of question we get very often in this forum, but here goes.

AVAST - www.avast.com and AVG www.avg.com offer the most popular free anti-virus software I know of ... in terms of downloads. I'm sure free versions of Mcafee and Norton are also available, among others. I use a MacBookPro, most of the time ... so it's hasn't really been a concern.

Cheers,

Mike