In the 28 years I've used Mac's I've had three viruses. One was actually injected by an IT person [accidentally] maintaining our Mac's at work. We had about 45,000 Macs at that time spread over four continents.
Having worked in software...
My AV application, Virus Barrier X6. I had tens of thousands of log files with a first line something like this
mdworker(9642) deny mach-lookup com.intego.mig_hook
The number of such files is equal to the difference between my "normal"...
I upgraded to ML a couple of days after the release. It seemed to work fine and the only thing I noticed was that the number of files on my HD went from about 300K to about 900K. I started a plot of the file count and the HD space....