airgap

An air gap is a physical separation intended to prevent communication or contamination between two systems or conduits. In information technology, an air-gapped system is one that is physically isolated from unsecured networks, including the internet, and from most other networks. This isolation is used to reduce exposure to cyber threats in high-security environments such as national defense, critical infrastructure, finance, and certain laboratories. In practice, air-gapped systems operate without direct network connectivity; updates and data transfers are performed through controlled, manual processes, often via removable media or dedicated transfer stations.

The principal advantage of air-gapped systems is the substantial reduction of remote, large-scale cyber risk. Their operational burden, however, includes stringent procedures, limited update capabilities, and reliance on secure physical access. Despite the gap, air gaps are not foolproof. Malware can still be introduced through removable media, insider actions, or supply-chain compromises. In some cases, researchers and attackers have explored covert channels that exploit side channels—such as power fluctuations, electromagnetic emissions, acoustics, or timing—to exfiltrate data across the gap. Real-world breaches typically involve multiple steps and a carefully prepared attack chain, underscoring that air gaps raise security but do not guarantee it.

In plumbing and building services, the term air gap also refers to a physical separation that prevents backflow from a downstream outlet into a potable water supply. This backflow prevention measure is essential for maintaining water quality and is implemented via devices designed to create a vertical or atmospheric separation between outlets and the supply line.