What is a man-in-the-middle attack?
In a man-in-the-middle attack, the attacker intercepts traffic between a client and server, and impersonates the client to the server, and vice-versa. In a man-in-the-middle attack, an attacker Charles intercepts traffic between Alice and Bob. Charles impersonates Bob to Alice, and simultaneously impersonates Alice to Bob. Alice has an encrypted channel to Charles, and Charles has an encrypted channel to Bob, but Charles can decrypt and possibly modify traffic in either direction before forwarding it. A technical description appears in RSA Laboratories’ Frequently Asked Questions About Today’s Cryptography (http://www.rsasecurity.com/rsalabs/faq/3-6-1.
