pcAnywhere 8.x and 9.0 allows remote attackers to cause a denial of service via a TCP SYN scan, e.g. by nmap.
http://www.iss.net/security_center/static/4347.php
http://archives.neohapsis.com/archives/bugtraq/2001-02/0258.html
http://archives.neohapsis.com/archives/bugtraq/2001-02/0201.html