Definition
An air gap is a security measure where a computer or network is physically isolated from other networks, especially unsecured ones like the internet. This separation means there is no direct physical or logical connection, preventing unauthorized access or data transfer. In practice, data is moved between the air-gapped system and external networks using removable media like USB drives, which are carefully scanned for threats. This isolation is crucial for protecting highly sensitive information or critical infrastructure from cyberattacks. For instance, nuclear launch control systems or top-secret government networks are often air-gapped. Unlike a demilitarized zone (DMZ) which sits between networks, an air gap completely severs connections. This concept is fundamental to cybersecurity and appears on exams like Security+, CySA+, and CISSP.