networking A dedicated gateway machine with special security

precautions on it, used to service outside network, especially

Internet, connections and dial-in lines. The idea is to

protect a cluster of more loosely administered machines hidden

behind it from crackers. The typical firewall is an

inexpensive microprocessor-based Unix machine with no

critical data, with modems and public network ports on it, but

just one carefully watched connection back to the rest of the

cluster. The special precautions may include threat

monitoring, call-back, and even a complete iron box

keyable to particular incoming IDs or activity patterns.