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A dedicated gateway machine with special securityprecautions on it, used to service outside network, especiallyInternet, connections and dial-in lines. The idea is toprotect a cluster of more loosely administered machines hiddenbehind it from crackers. The typical firewall is aninexpensive microprocessor-based Unix machine with nocritical data, with modems and public network ports on it, butjust one carefully watched connection back to the rest of thecluster. The special precautions may include threatmonitoring, call-back, and even a complete iron boxkeyable to particular incoming IDs or activity patterns.Firewalls often run proxy gateways.Synonym flytrap, Venus flytrap.