source: http://www.securityfocus.com/bid/1414/info

Microsoft Windows 2000 Server comes with a telnet server to provide remote console access. A remote attacker can send a stream of binary zeros to the server, causing it to fail. If automatic restart is enabled, numerous attacks will cause the telnet server to restart until the maximum failure/restart count is exceeded, at which point the service is disabled. 

An attacker can exploit this issue using netcat under Linux:

nc target.host 23 < /dev/zero