If you have not patched yet for vulnerability MS11-100 you might want to do it ASAP, because the DoS PoC exploit for this vulnerability has been published two days ago.

More information about the vulnerability and patches at http://technet.microsoft.com/en-us/security/bulletin/ms11-100

Manuel Humberto Santander Peláez
SANS Internet Storm Center - Handler
Twitter: @manuelsantander
Web:http://manuel.santander.name
e-mail: msantand at isc dot sans dot org