Air Gap
Air Gap
Air Gap (physische Netztrennung)
An air gap is the complete physical separation of a system or network from all other networks, especially from the internet. The idea: what is not connected cannot be attacked remotely either. In practice, however, this separation is rarer and more permeable than many assume.
History & facts. Air gaps are used for especially worthy-of-protection environments — such as in industry, at utilities or in military areas. But the supposedly absolute security is deceptive: Stuxnet overcame an air gap in 2010 by carrying itself via USB media into an isolated facility. Maintenance laptops, remote-maintenance access, mobile data carriers and simply poorly implemented separations regularly undermine the concept too. Research also shows exotic ways to smuggle data via sound, light or electromagnetic emanation — practically laborious, but possible.
Outlook & recommendation. An air gap is a valuable building block but no panacea; it must be maintained with discipline. Decisive is the strict control of all transitions: removable media, maintenance access and temporary connections are the typical break points. Behind an air gap too, visibility and monitoring are needed, for once an attacker is inside, all detection is otherwise missing. The concept is thus a complement to segmentation and access control, not a substitute for them.