The F variant of Mydoom was found four days ago. A bit surprisingly, we've started seeing it in bigger numbers today. We're currently considering issuing a Level 2 Radar alert on it.

The F variant is important, as in addition of spreading, installing backdoors and launching DDoS attacks (like the previous variants), it also randomly deletes data files with these extensions: DOC, XLS, MDB, JPG, BMP, AVI and SAV.