1. X firewall proxy server The X firewall proxy is an application layer gateway proxy that may be run on a network firewall host to forward X traffic across the firewall. Used in conjunction with the X server Security extension and authorization checking, xfwp constitutes a safe, simple, and reliable mechanism both to hide the addresses of X servers located on an intranet and to enforce a server connection policy. Xfwp cannot protect against mischief originating on an intranet; however, when properly configured it can guarantee that only trusted clients originating on authorized external Internet hosts will be allowed inbound access to local X servers. From Debian 3.0r0 APT