All electrical, electronic and electromechanical devices, caused by their nature, emit electromagnetic energy to their surroundings while working. TEMPEST is a term expressing  “classified” information unintentionally arising from electrical and electronic equipment, electromagnetic energy propagation and diffusion, and investigation, examining and controlling of this emanations.

Contrary to the widely known, TEMPEST is not an acronym. It is a “code name” which is firstly used by the National Security Agency (NSA) of U.S. Emanations of the information processed in electrical devices by electromagnetic radiation was first discovered by U.S. in the 1950’s, the British intelligence agency was aware of the issue in 1960’s. First public test about TEMPEST was made ​​in 1985 by a Dutch engineer, Van Eck,  and has been published. Studies on this topic in Turkey, especially in TUBITAK (Scientific and Technological Council of Turkey) is carried out since the 90’s, and awareness of the issue is increasing rapidly especially in public institutions…

TEMPEST is a natural result of EMI, Electromagnetic Interference. Therefore the counter-measures to be taken is very similar to solve the problem of electromagnetic interference. A processing IT equipment (computer, monitor, printer, scanner, copier, etc..) makes a radiation  using the atmosphere (space) and has a conducted emission using the cables running through the device. Thus the information processed by the source device at that time can be collected from a distance of propagation by receiver antennas, probes, etc. and  the information can be accessed. Spatial energy emitted by radiation from a distance can be accessed from about a hundred yards however this distance becomes to ranges kilometers if the leakage occurs through conductivity .

To obtain the TEMPEST leakage of electromagnetic energy from the source directly, you need to reach any connected conductor of the source, though, in the case of indirect TEMPEST leaks, the sufficient thing is just to reach a conductor running nearby the source device or cable. For example, considering the target source as a computer any fortuitous conductor passing at closer than a certain distance (telephone cables, water pipes, heating apparatus etc..) can collect the radiation as a receiving antenna and can carry the information to unauthorized persons or uncontrolled regions.

TEMPEST countermeasures covers a variety of improvements in the equipments used and special arrangements and precautions for the buildings or installations in buildings. For the countermeasures, national or international documents (standards, guidelines, etc.) explainig the tests to be done to the equipments and buildings, restricting building installation practices are used. They are most commonly military documents.

Shielding (screening, Faraday cage practice), bonding and grounding are the most favorable methods against radiated information leakages where for the conducted TEMPEST emissions, problem can be overcome with filtering. TEMPEST featured filter is basically a device that allows the signals that must pass through a conductor and stops (attenuates)  the unwanted signals (TEMPEST leakage) according to the standards rules. The most reliable solution to cleanse ourselves from TEMPEST threat is to use briefly TEMPEST proof equipment (computers, printers, scanners, keyboards, etc..). These devices are designed and developed nationally at TÜBİTAK – UEKAE in Turkey.

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