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An air gap, air wall, air gapping or disconnected network is a network security measure 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.¹⁾. It means a computer or network has no network interfaces connected to other networks, with a physical or conceptual air gap, analogous to the air gap used in plumbing to maintain water quality.

An “air-gapped” computer or network is one that has no network interfaces, either wired or wireless, connected to outside networks. Many computers, even when they are not plugged into a wired network, have a wireless network interface controller (WiFi) and are connected to nearby wireless networks to access the Internet and update software. This represents a security vulnerability, so air gapped computers either have their wireless interface controller permanently disabled or physically removed. To move data between the outside world and the air-gapped system, it is necessary to write data to a physical medium such as a thumbdrive, and physically move it between computers. Physical access is easier to control than an electronic network interface, which can be attacked at any time from the exterior insecure system and, if malware infects the secure system, can be used to export secure data.

Air gap (networking)