I think it’s mildly amusing how many years when I was using Windows for Workgroups 3.11 in a 16 bit interface on top of DOS, that even back then. Microsoft had AntiVirus Software you could use in your WFW3.11 installation. It wasn’t until a year or so later they stopped development and then McAffee came to the rescue along with Nortons AntiVirus.
Now move forward 13 years and Microsoft has started AntiVirus Software development for the Windows platform on Corporate & Consumer products.
Now I wonder if they will ever restart development on Mac OS X for Internet Explorer. Pipe dreams I guess but I must admit I used it on Mac OS before Apple released Mac OS X.