The Trend Micro OfficeScan client allows remote attackers to cause a denial of service by making 5 connections to port 12345, which raises CPU utilization to 100%.
http://www.securityfocus.com/bid/1013
http://www.antivirus.com/download/ofce_patch_35.htm
http://archives.neohapsis.com/archives/bugtraq/2000-02/0340.html