I am well aware of Sophos anti-virus for Mac as well as all the others. . . and the fact is that the virus and worms it finds are all WINDOWS viruses and worms. ,p> To do that, it TURNS OFF the built in Apple Gatekeeper which blocks all of the 67 known OS X TROJANS and variants and all 8 of the trojan families so that Sophos can intercept them instead.
Gatekeeper will warn the OS X user before he can finish downloading the infected file, requiring an administrator's name and password before continuing, If the user does that, it then require the name and password again before installing it, and then again before allowing it to be run.
Yet all of the OS X 3rd party anti-virus software turns that off, AND adds system hits and performance degradation to do essentially the same thing as what the Gatekeeper does without that overhead. . . just so you can catch some Windows viruses and worms that can't harm an OS X Mac at all.
But that is neither here-nor-there with what this article was about.