SOCKS proxy

En mi curro nos han estado cambiando la configuracion del firewall, de manera que el yahoo messenger ya no chiscaba. Cambiando la configuracion para usar un socks proxy, ha funcionado. ¿Pero que es un socks proxy?

Socks (or "SOCKS") is a protocol that a proxy server server can use to
accept requests from client users in a company's network so that it can
forward them across the Internet. Socks uses sockets to represent and
keep track of individual connections. The client side of Socks is built
into certain Web browsers and the server side can be added to a proxy
server.

A socks server handles requests from clients inside a company's firewall
and either allows or rejects connection requests, based on the requested
Internet destination or user identification. Once a connection and a
subsequent "bind" request have been set up, the flow of information
exchange follows the usual protocol (for example, the Web's Hypertext
Transfer Protocol protocol).

Parece que aqui hay bastante informacion sobre el protocolo.