Back on Oct. 23, 2008, Microsoft released a critical security update for Windows: MS08-067. Isolated attacks existed at the time of the bulletin release and in our blog we strongly recommended installing the security update as quickly as possible. Later, a few trojans that exploit this vulnerability were found and a month from the release of the bulletin we blogged again, this time about the first worm which exploited that vulnerability: Win32/Conficker (here and then here).
Over the last couple of weeks, a new variant of this worm has been affecting customers. We detect it as Worm:Win32/Conficker.B. In addition to exploiting MS08-067, this variant also uses other propagation methods; it tries to copy itself to network shares by guessing their passwords. If the password is weak, it may succeed. It also tries to spread via removable media.
Via : http://blogs.technet.com/mmpc/archive/2009/01/13/msrt-released-today-addressing-conficker-and-banload.aspx
