Jim Hamm started off with a link http://www.slashgear.com/avg-antivirus-for-mac-launches-with-triple-protection-12308577/ about AVG AntiVirus protection, but that raised a few questions. Have you used this? Will it run on Mac running an earlier system? Jim obliged with more info, "I haven't used AVG, but it's been around for a long time and has a good reputation. It will run on Mavericks and Mountain Lion. Here's some more info on AVG."
But Jim, what antivirus program are you now using? "I use Avast AV, which is also free."
So, there you have it. Any more questions from anybody? Any recommendations? Let's keep up on what works!