Air gap (networking)

An air gap or air wall is a network security measure, also known as air gapping, employed on one or more computers to ensure that a secure computer network is physically isolated from unsecured networks, such as the public Internet or an unsecured local area network. The name arises from the technique of creating a network that does not have, and often has never had, an active unsecured connection, by having the two physically separated, with air in between. The air gap may not be completely literal, as networks employing the use of dedicated cryptographic devices that can tunnel packets over untrusted networks while avoiding packet rate or size variation can be considered "air gapped", as there is no ability for computers on opposite sides of the "gap" to communicate.