air gap
termsecuritynetworking
Isolating a system by giving it no network connection at all: the security control made of literal absence.
Air-gapped networks protect industrial control, classified, and backup systems by ensuring no cable or radio reaches them; data crosses only by escorted media. Stuxnet is the canonical proof of the limits, walking into isolated centrifuge controllers on USB sticks, and researchers keep demonstrating exotic exfiltration through sound, heat, and blinking LEDs. The gap raises the attacker's cost enormously without reducing the defender's need for discipline: the moment convenience wins one exception, the gap is a story you tell auditors.