A new threat dubbed Doomjuice, a semi-variant of the MyDoom virus, has been spreading on the internet, in particular targeting the Microsoft website and being successful in slowing it down.
The new strain is hunting computers infected with either the earlier MyDoom A or B viruses but is moving noticeably slower than its predecessors. This version doesn't spread through email, a big difference from the MyDoom parent.
Microsoft have given it the name of MyDoom C and has been fending off data requests to its website, designed to overload the site and ultimately bring it down. Source