1. In communications, a proxy is something that acts as a server, but when given requests from clients, acts itself as a client to the real servers. Analogy: Consider talking to somebody who speaks a foreign language through a translator. You talk to the translator, who receives your statements, then regenerates something else completely to the other end. The translator serves as your proxy. Key point: The communication terminates at the proxy. In other words, the proxy doesn't forward data so much as it tears it completely apart. For example, an HTTP proxy doesn't forward every request sent through it. Instead, it first examines if it already has the requested web page in its cache. If so, then it returns that page without sending another request to the destination server. Because proxies completely terminate the communication channel, they are considered a more secure firewall technology than packet filters, because they dramatically increase the isolation between the networks. Key point: You will occasionally be scanned for proxies. ISPs scan their users for proxies. Hackers scan the Internet looking for proxies they can anonymize their connections with. Certain servers (like IRC servers) scan clients for proxies in order to prevent anonymous connections. Several websites maintain lists of such proxies. e.g. http://proxys4all.cgi.net/ From Hacking-Lexicon