DISABLE - Turn off or disable Proxy checking.
ENABLE - Turn on or enable Proxy checking.
LIST - List proxycheck settings..
PORT - Specify specific ports to be scanned.
REASON - Set the reason that a client gets disconnected.
REPORT - Set reporting options.
SET - Set specific proxycheck settings.

The proxycheck command allows you to control the built-in proxy server scanner to prevent abuse on the server from people using insecure wingates or proxies. When a connection is attempted, the scanner will attempt to establish a connection back to the client, and verify that no insecure proxy server is installed on the system. If a proxy server is detected, options are available to specify what action should be taken.

Note: this option will require at 1 TCP connection attempt to be made to the user, for each protocol and each port that is scanned for.

/as help security proxycheck <topic>

Proxy checking is highly recommended. Insecure proxies and wingates allow users to go through other people's connections to cause problems. This gives the actual abuser anonymity. People with unsecured proxies generally are simply uneducated about how to run a secure one. They will usually fix the problem once they understand it and what they need to do.