source: http://www.securityfocus.com/bid/1798/info

The Remote Desktop Sharing component of Microsoft NetMeeting for Windows NT 4.0 / 2000 does not properly handle a particular type of malformed input string sent over port 1720. CPU utilization can be caused to spike to 100% and any existing NetMeeting sessions would fail in the event of an attack. Restarting the application would be required in order to regain normal functionality.

NetMeeting, including the affected component Remote Desktop Sharing, is shipped with Microsoft 2000 but is not enabled by default. NetMeeting can be downloaded as an add-on for NT 4.0.

*A new variant of this vulnerability has been discovered, the result of the new variant is the same as the originally discovered issue. No further technical details have been made available. User's are encouraged to install the latest patch.

nc target 1720 < /dev/zero