Tor is service that provides for anonymous connections over the Internet. The name Tor is formed from the expression "the onion router". Tor operates by selecting routers from its system at random to create an end-to-end pathway. Then, each router sends a public key for message encryption. The message is encrypted by each router's public key in turn. As a message comes to a router, the router decrypts the message with its private key. The effect is of peeling off encryption in layers - hence the idea of the onion router.
The Tor service is free and the client software is open source. Tor supports SOCKS-aware applications.
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