WS_FTP Pro 6.0 uses weak encryption for passwords in its initialization files, which allows remote attackers to easily decrypt the passwords and gain privileges.
http://www.securityfocus.com/bid/547
http://www.ntbugtraq.com/default.asp?pid=36&sid=1&A2=ind9907&L=ntbugtraq&D=0&P=10370&F=P