Here's an embarrassing one, security firm Alternative Computer Technology appears to have got infected with the Nimda virus which not only infects Windows PCs but also sticks itself on Web servers, so some browsers pick it up automatically when they visit an infected site.
As a Web security firm though, you'd expect ACT to know better. Last time we looked, a file of exactly the same file size as the virus could be located at www.altcomp.com/readme.eml. We don't suggest downloading it.
Also, according to some reports Nimda is the most sophisticated worm yet - mostly because it combines a whole range of other worm characteristics. ®