Tempest (codename)

TEMPEST is a U.S. National Security Agency specification and a NATO certification[1][2] referring to spying on information systems through leaking emanations, including unintentional radio or electrical signals, sounds, and vibrations.[3][4] TEMPEST covers both methods to spy upon others and how to shield equipment against such spying. The protection efforts are also known as emission security (EMSEC), which is a subset of communications security (COMSEC).[5]

The NSA methods for spying on computer emissions are classified, but some of the protection standards have been released by either the NSA or the Department of Defense.[6] Protecting equipment from spying is done with distance, shielding, filtering, and masking.[7] The TEMPEST standards mandate elements such as equipment distance from walls, amount of shielding in buildings and equipment, and distance separating wires carrying classified vs. unclassified materials,[6] filters on cables, and even distance and shielding between wires or equipment and building pipes. Noise can also protect information by masking the actual data.[7]

While much of TEMPEST is about leaking electromagnetic emanations, it also encompasses sounds and mechanical vibrations.[6] For example, it is possible to log a user's keystrokes using the motion sensor inside smartphones.[8] Compromising emissions are defined as unintentional intelligence-bearing signals which, if intercepted and analyzed (side-channel attack), may disclose the information transmitted, received, handled, or otherwise processed by any information-processing equipment.[9]