I generally don’t run antivirus software, because I’m not a likely target. I use up-to-date software and am careful about what I download and install. That said, there are plenty of people for whom antivirus software is important. It’s great to see: ClamWin Antivirus. A Free Open Source (GPL) Virus Scanner for Windows. This always seemed to me like the kind of thing that would work well as open source. Once you get the basic software put together (a non-trivial task, to be sure), updating the definitions is not quite so hard. There are plenty of security folks out there who follow these things, and I’m sure many of them would love to have the power to help stop viruses ASAP. Here’s that chance!