@Gojirax
I wonder why they picked KB921883 to freak out about?
Affected TCP/IP ports:
139 - NetBIOS Datagram Service
445 - Microsoft-DS
Basically, if you're running a Windows NetBIOS (SMB/CIFS) network without a firewall or MS' latest patches, you're vulnerable.
If you're doing -any- Windows Printer/File Sharing, you're running with these ports open.
This affects a -lot- of Windows networks. Maybe even DHS' own network. ;-)