Air gap (computing)

An air gap is a security measure often taken for computing installations that must be extraordinarily secure. It consists of ensuring that a secure network is completely physically, electrically, and electromagnetically isolated (e.g. no wireless connections to or from the secure network nor EM leakage (TEMPEST) from the secure network) from insecure networks, such as the public Internet or an insecure local area network. The upside to this is that such a network can generally be regarded as a closed system (in terms of information, signals, and emissions security) unable to be accessed from the outside world. The downside is that transferring information (from the outside world) to be analyzed by computers on the secure network is extraordinarily labor intensive, often involving human security analysis of prospective programs or data to be entered onto air-gapped networks and possibly even human manual re-entry of the data following security analysis.
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