packet sniffer
n. Software that monitors network traffic to steal passwords, credit card numbers, and other sensitive data. Also, the person who uses such software.

Example Citation:
Computer systems connected to networks, such as the Internet, are also vulnerable to sniffing: eavesdropping on communications between computers. Special software called packet sniffers can be connected to a computer network and extract all the packets of information used to pass data between computers.
—John Graham-Cumming, “Computing and the net: Attack of the Trojan Smurfs,“ The Guardian, March 12, 1998

Earliest Citation:
This paper describes an active attack against the Transport Control Protocol (TCP) which allows a cracker to redirect the TCP stream through his machine thereby permitting him to bypass the protection offered by such a system as a one-time password [skey] or ticketing authentication [kerberos]. The TCP connection is vulnerable to anyone with a TCP packet sniffer and generator located on the path followed by the connection.
—Laurent Joncheray, “Simple Active Attack Against TCP“,> Merit Network, January 20, 1994

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