The login interface in Symantec Enterprise Firewall 6.x, when a VPN with pre-shared key (PSK) authentication is enabled, generates different responses depending on whether or not a username is valid, which allows remote attackers to enumerate valid usernames.
https://exchange.xforce.ibmcloud.com/vulnerabilities/36081
http://www.vupen.com/english/advisories/2007/2909
http://www.symantec.com/avcenter/security/Content/2007.08.16.html
http://www.securitytracker.com/id?1018578