We’ve had reports of a new worm in the wild and that generates increased RDP traffic for our users on port 3389. Although the overall numbers of computers reporting detections are low in comparison to more established malware families, the traffic it generates is noticeable. The worm is detected as Worm:Win32/Morto.A and you can see a detailed description of at http://www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=Worm%3aWin32%2fMorto.A.
Morto attempts to compromise Remote Desktop connections in order to penetrate remote systems, by exploiting weak administrator passwords. Once a new system is compromised, it connects to a remote server in order to download additional information and update its components. It also terminates processes for locally running security applications in order to ensure its activity continues uninterrupted. Affected users should note that a reboot may be required in order to complete the cleaning process.