When it infects a system, MyDoom.B automatically sends emails to all of the victim's email contacts, blocks access to antivirus vendor Web sites and Microsoft's site, leaves a backdoor, and is designed to launch an attack against www.microsoft.com next month, according to the software giant.
Microsoft urged people with information about the worm to contatct the FBI, Secret Service, Interpol, or the Internet Fraud Complaint Center.
In November, Microsoft launched a $5 million reward program in an effort to catch virus writers.