For years I have used the following explanation when people ask me why Microsoft doesn't bundle antivirus software: Although Microsoft has never ruled out the notion of adding antivirus software to its offerings in the past, it has had no real bottom-line reason to do so. Microsoft does not do anything unless it fends off a threat to the core business or makes money. So why develop a huge company infrastructure to support antivirus software? There is no way Microsoft could sell the software, because people would demand that it be bundled as part of the operating system. And Microsoft would have to do that anyway, to have a consistent story about how it innovates. So where is the additional revenue? With antivirus software, there is none: It's just an added expense.

So, I was just as surprised as anyone else when Bill Gates told a small group having dinner with him in Manhattan just before the launch of Windows XP that the company may be reconsidering its position on the issue. Note that Microsoft is already toying with building firewall protection into the OS, as with Windows XP. There doesn't seem to be any money in that either. So what's going on? I think Microsoft will incorporate antivirus software into its system for marketing reasons that are directly related to the company's .NET strategy. I also suspect that Microsoft will license the software from an existing antivirus company and put it under the Microsoft label, but that's not important. What is important is the underlying reason for all this—and it's not computer security.