SOCKSA protocol for handling TCP traffic through a proxy server. It can be used with virtually any TCP application, including Web browsers and FTP clients. It provides a simple firewall because it checks incoming and outgoing packets and hides the IP addresses of client applications.
There are two main versions of SOCKS -- V4 and V5. V5 adds an authentication mechanism for additional security. There are many freeware implementations of both versions. One of the most common V5 implementations is SOCKS5, developed by NEC.
SOCKS was recently accepted as an IETF standard and is documented in RFC 1928, 1929 and 1961.