1.6 Active vs. Passive Attacks
A passive attack is one in which the intruder eavesdrops but does not modify the message stream in any way. An active attack is one in which the intruder may transmit messages, replay old messages, modify messages in transit, or delete selected messages from the wire. A typical active attack is one in which an intruder impersonates one end of the conversation, or acts as a man-in-the-middle (see §6.4.1 The Bucket Brigade/Man-in-the-Middle Attack).