An air-gapped network is a system or network kept physically separate from the internet and other external links. The goal is to reduce the attack surface by preventing direct remote access, so data and commands cannot simply travel over normal network paths.
Air gaps matter because they are often used for sensitive environments such as industrial control, research, government, or defense systems. In real attacks, adversaries try to break the isolation indirectly through removable media, infected laptops, shared files, or trusted operators who move data between zones. That is why an air gap is a strong barrier, but not a complete guarantee. Defenders pair it with strict USB control, media scanning, device whitelisting, logging, and procedures that limit what can cross the boundary. When a threat report mentions “propagation into isolated networks,” it usually means the attacker is trying to exploit those human or media-based bridges.