Measurement and signature intelligence

Measurement and Signature Intelligence, or MASINT, refers to intelligence gathering activities that bring together disparate elements that do not fit within the definitions of Signals Intelligence (SIGINT), Imagery Intelligence (IMINT), or Human Intelligence (HUMINT).

According to the United States Department of Defense, MASINT is technically derived intelligence (excluding traditional imagery IMINT and signals intelligence SIGINT) that – when collected, processed, and analyzed by dedicated MASINT systems – results in intelligence that detects, tracks, identifies, or describes the signatures (distinctive characteristics) of fixed or dynamic target sources. MASINT was recognized as a formal intelligence discipline in 1986. .

It can be difficult to draw a line between tactical sensors and strategic MASINT sensors. Indeed, the same sensor may be used tactically or strategically. In a tactical role, a submarine might use acoustic sensors -- active and passive sonar -- to close in on a target or get away from a pursuer. Those same passive somars may be used by a submarine, operating stealthily in a foreign harbor, to characterize the signature of a new submarine type.

As with many intelligence disciplines, it can be a challenge to integrate the technologies into the active services, so they can be used by warfighters .

One of the great hopes for MASINT was Non-Cooperative Target Recognition, which could, even with the failure of IFF systems, prevent friendly fire incidents. One problem of such identification is when coalition partners use the same equipment, as did both Iraq and Syria have Russian T-72 tanks and French aircraft during Desert Storm.

Even though today's MASINT is often on the edge of technologies, many of them under high security classification, the techniques have a long history. Acoustic and optical methods for locating hostile artillery go back to the First World War.

Understanding "Measurement" and "Signature"

In the context of MASINT, measurement obtains finite metric parameters of targets.

Signature covers the distinctive features of phenomena, equipment, or objects as they are sensed by the collection instrument(s). The signature is used to recognize the phenomenon, equipment, or object once its distinctive features are detected. (IOSS Section 2) Another way to think of it is that a signature is a known norm, such as a normal blood sugar in medicine. MASINT measurement searches for differences from known norms, and characterizes the signatures of new phenomena. For example, the first time a new rocket fuel exhaust was measured, it would be a deviation from a norm. When the properties of that exhaust were measured, such as its thermal energy, spectral analysis of its light (i.e., spectrometry), etc., that becomes a new signature in the MASINT data base.

While there are specialized MASINT sensors, much of the MASINT discipline involves analysis of information from other sensors. For example, a SIGINT sensor may provide information on the specific characteristics and capabilities of a radar beam, which would be part of ELINT. That same sensor, however, may provide information about the "spillover" of the main beam (sidelobes), or interference its transmitter produces. Those incidental characteristics, are MASINT disciplines.

Putting these concepts together is challenging; MASINT specialists themselves struggle with providing simple explanations of their field . One attempt calls it the “CSI” of the intelligence community(BetterDef), in imitation of the television series “Crime Scene Investigation”. This is useful only to the extent that it emphasizes MASINT depends on a great many sciences to interpret data, where COMINT would deal with the meaning in an intelligible human message. Interpreting that message is not trivial, in that it would require idiomatic knowledge of the language involved, any specialized terminology being discussed, and inferences about emotional states and other subtle clues.

Another possible definition calls it “astronomy except for the direction of view” (BetterDef). The allusion here is to observational astronomy being a set of techniques that do remote sensing, through atmospheric interference with earthbound telescopes. Astronomers make observations in multiple electromagnetic spectra, ranging from radio waves, through infrared, visible, and ultraviolet light, into the X-ray spectrum and beyond. They correlate these multispectral observations and create hybrid, often “false-color” images to give a visual representation of wavelength and energy, but many of their more detailed information is more likely a graph of such things as intensity and wavelength versus viewing angle.

Another analogy uses medicine as a basis . If you have been weighed, that is a gravity measurement, which will be compared against signatures such as underweight, normal, and overweight for your height, age, and build. Gravity measurements proper fall under geophysical MASINT (HaveYou) Similarly, biopsies measure tissue samples against normal cell signatures, and are a form of materials MASINT.

Hearing tests involve acoustic MASINT. While the previous two "medical MASINT" measurements were passive, this was active, sending a signal to your ear. True MASINT measurements can be either active (e.g., radar or laser illumination) or passive (e.g., radiation detection or thermal scanning).

Organizational

Within the US Intelligence Community the Directorate of MASINT and Technical Collections office of the Defense Intelligence Agency is the central agency for MASINT. For education and research, there is the Center for MASINT Studies and Research of the Air Force Institute of Technology.

International Implications

All nuclear testing, of any level, was forbidden under the Comprehensive Test Ban Treaty (CTBT), but there is controversy over whether the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) will be able to detect sufficiently small events. It is possible to gain valuable data from a nuclear test that has an extremely low yield, useless as a weapon but sufficient to test weapons technology. CTBT does not recognize the threshold principle and assumes all tests are detectable.

The CTBTO will operate an International Monitoring System (IMS) of MASINT sensors for verification, which include seismic, acoustic, and radionuclide techniques. See National Means of Technical Verification for a discussion of the controversies surrounding the ability of the IMS to detect nuclear tests.

Disciplines

MASINT is made up of six major disciplines, but the disciplines overlap and intertwine. They interact with the more traditional intelligence disciplines of HUMINT, IMINT, and SIGINT.

An example of the interaction is ‘’imagery-defined MASINT (IDM)’’. In IDM, a MASINT application would measure the image, pixel by pixel, and try to identify the physical materials, or types of energy, that are responsible for pixels or groups of pixels: signatures. When the signatures are then correlated to precise geography, or details of an object, the combined information becomes something greater than the whole of its IMINT and MASINT parts.

The Center for MASINT Studies and Research breaks MASINT into:

• Nuclear radiation (alpha, beta, gamma, neutron)
• geophysical (seismic, acoustic, magnetic),
• radar (OTH,SAR,LOS),
• radiofrequency (RINT (unintentional radiation) and EMP),
• electro-optical (ON IR, spectral, laser) IRINT
• materials (chemical, biological, nucler) CBINT

Electro-optical MASINT

MASINT collection technologies in this area use radar, lasers, staring arrays in the infrared and visual, to point sensors at the information of interest. As opposed to IMINT, MASINT electro-optical sensors do not create pictures. Instead, they would indicate the coordinates, intensity, and spectral characteristics of a light source, such as a rocket engine, or a missile reentry vehicle.

Observation of foreign missile tests, for example, make extensive use of MASINT along with other disciplines. For example, electro-optical and radar tracking establish trajectory, speed, and other flight characteristics that can be used to validate the TELINT telemetry intelligence being received by SIGINT sensors. Closely coupled electro-optical sensors and radards work from platforms on aircraft (e.g., US RC-135 COBRA BALL), ground stations (e.g., US COBRA DANE) and ships (e.g., US COBRA JUDY).

Electro-optical MASINT (FM2-0Ch9) involves obtaining information from emitted or reflected energy, across the wavelengths of infrared, visible, and ultraviolet light

While IMINT operates in these wavelengths, MASINT does not “take pictures” in the conventional sense, but it can validate IMINT pictures. A classic example of validation would be analyzing the detailed optical spectrum of a green area in a photograph: is the green from natural plant life, or is it camouflage paint? The electro-optical techniques of MASINT include measurement of the radiant intensities, dynamic motion, and the materials composition of a target. These measurements put the target in spectral and spatial contexts. Sensors used in electro-optical MASINT include radiometers, spectrometers, non-literal imaging systems, lasers, or laser radar (LIDAR). (FM2-0Ch9)

Infrared MASINT (IRINT)

Infrared MASINT excludes IMINT using the infrared spectrum, but can complement that IMINT by validating targets by not only their shape, but by their reflected spectrum and their thermal characteristics.

LASER MASINT (LASINT)

Integration and specialized application of MASINT E-O and other collection to gather data on laser systems. The focus of the collection is on laser detection, laser threat warning, and precise measurement of the frequencies, power levels, wave propagation, determination of power source, and other technical and operating characteristics associated with laser systems¾ strategic and tactical weapons, range finders, and illuminators. (FM2-0Ch9) In addition to passive measurements of other lasers, the MASINT system can use active lasers (LIDAR) for distance measurements, but also for destructive remote sensing that provides energized material for spectroscopy. Close-in lasers could do chemical (i.e., materials MASINT) analysis of samples vaporized by lasers.

Spectroscopic MASINT

Spectroscopy can be applied either to targets that are already excited, such as an engine exhaust, or stimulated with a laser or other energy source. The results plot energy versus frequency. A spectral plot represents radiant intensity versus wavelength at an instant in time. The number of spectral bands in a sensor system determines the amount of detail that can be obtained about the source of the object being viewed. Sensor systems range from multispectral (2 to 100 bands) to hyperspectral (100 to 1,000 bands) to ultraspectral (1,000+ bands). More bands provide more discrete information, or greater resolution. The characteristic emission and absorption spectra serve to fingerprint or define the makeup of the feature that was observed. A radiometric plot represents the radiant intensity versus time. An example is the radiant intensity plot of a missile exhaust plume as the missile is in flight. The intensity or brightness of the object is a function of several conditions including its temperature, surface properties or material, and how fast it is moving. For each point along a time-intensity radiometric plot, a spectral plot can be generated based on the number of spectral bands in the collector. (FM2-0Ch9 & pp 1-2)

Hyperspectral Imagery MASINT

A subcategory of E-O intelligence produced from reflected or emitted energy in the visible and near infrared spectrum used to improve target detection, discrimination, and recognition. HSI can detect specific types of foliage¾ supporting drug-crop identification; disturbed soil¾ supporting the identification of mass graves, minefields, caches, underground facilities or cut foliage; and variances in soil, foliage, and hydrologic features¾ often supporting NBC contaminant detection.

Space-based Staring Infrared Sensors

The US, in 1970, launched the first of a series of space-based staring array sensors that detected and located infrared heat signatures, typically from rocket motors but also from other intense heat sources. Such signatures, which are associated with measurement of energy and location, are not pictures in the IMINT sense. Currently called the Satellite Early Warning System (SEWS), the program is the descendant of several generations of Defense Support Program (DSP) spacecraft.

Originally intended to detect the intense heat of an ICBM launch, this system proved useful at a theater level in 1990-1991. It detected the launch of Iraqi Scud missiles in time to give early warning to potential targets.

Radar MASINT

Specialized MASINT radar techniques include line-of-sight (LOS), over-the-horizon, synthetic aperture (SAR), inverse synthetic aperture (ISAR) and multistatic.

The active or passive collection of energy reflected from a target or object by LOS, bistatic, or over-the-horizon radar systems. RADINT collection provides information on radar cross-sections, tracking, precise spatial measurements of components, motion and radar reflectance, and absorption characteristics for dynamic targets and objectives.

(Ives & pp 9-10) observes that radar has characteristics especially appropriate for MASINT. While there are radars (ISAR) that can produce images, radar pictures are generally not as sharp as those taken by optical sensors, but radar is largely independent of day or night, cloud or sun. Radar can penentrate many materials, such as wooden buildings.

Radar generally must acquire its images from an angle, which often means that it can look into the sides of buildings, producing a movie-like record over time. Radar can also merge with other sensors to give even more information.

Synthetic aperture radar (SAR) MASINT

A Synthetic aperture radar (SAR) system, coupled with other MASINT and IMINT sensors, can, provide a high resolution, day and night collection capability. Recorded over time, it can be excellent for tracking changes.

In addition, it has ground- and water-penetrating capability, and is good for picking objects out of deliberate or natural clutter.

Line-of-sight Radar MASINT

Methods continue to evolve. COBRA JUDY is intended to gather information on long-range missiles, in a strategic role. One developmental system, COBRA GEMINI, is intended to complement COBRA JUDY. It can be used for observing long-range missiles, but is also appropriate for theater-level weapons, which may be addressed in regional arms limitation agreements, such as the Missile Technology Control Regime (MCTR). Where COBRA JUDY is built into a ship, this dual frequency (S- and X-band) radar is transportable, capable of operating on ships or on land, and optimized for monitoring medium range ballistic missiles and antimissile systems. It is air-transportable to deal with sudden monitoring contingencies.

Multistatic Radar MASINT

Multistatic methods are one of the most powerful techniques for defeating low-observability "stealth" technologies. Here, we are concerned with physically separated radar transmitters and receivers, precisely synchronized to a common time reference.

Materials intelligence

Materials intelligence, involving the collection, processing, and analysis of gas, liquid, or solid samples, is critical in defense against chemical, biological, and radiological threats, as well as more general safety and public health activities.

Samples are both collected by automatic equipment, such as air samplers, and directly by humans. Samples, once collected, may be rapidly characterized or undergo extensive forensic laboratory analysis to determine the identity and characteristics of the sources of the samples.

Chemical MASINT

There are a wide range of reasons to do chemical analysis of substances to which one's own forces are exposed, as well as learning the nature and signatures of a wide range of chemicals used by other nations.

Ammunition, Explosive, and Rocket Propellant Analysis

Traditional chemical analysis, as well as techniques such as spectroscopy using remote laser excitation, are routine parts of technical intelligence.

Chemical Warfare

Since the advent of chemical warfare in the First World War, there has been an urgent operational requirement for detecting chemical attacks. Early methods depended on color changes in chemically treated paper, or even more lengthy and insensitive manual methods.

Modern chemical weapon detection is highly automated. One technique involves continual sampling of air through a nondispersive infrared analyzer. More complex instrumentation, such as gas chromatographs coupled to mass spectrometers, are standard laboratory techniques that need to be modified for the field.

Biological analysis

In modern materials analysis, the line between chemical and biological methods can blur, since immunochemistry, an important discipline, uses biologically created reagents to detect chemical and biological substances.

Biological Warfare Detection

A wide range of techniques, some similar to those used in biomedical laboratories, but others modified for field use, can be used to detect biological warfare. One technique uses enzyme-linked immunosorbent analysis ELISA on particles filtered from the air.

Flow cytometry is another biological detection technique that can be used on liquids.

Personnel detectors

A Vietnam-era sensor, the XM2, generally known as the "people sniffer", detected ammonia concentrations in air, which indicated the presence of groups of people or animals. While it was sensitive, but not selective for people, many water buffalo became targets. Nevertheless, it was considered the best sensor used by the 9th Infantry Division, because, as opposed to other MASINT and SIGINT sensors, it could give helicopter-borne troops real-time detection of targets The authors compared the timeliness of a range of sensors {{Harv } Sharpen | p. 97, Chart 10}} (Figure)

Nuclear test analysis

Monitoring nuclear tests involves both chemical analysis, part of materials MASINT, and analysis of the radioactive emissions of samples, which crosses materials and nuclear MASINT. Not all nuclear MASINT involves materials analysis; see space-based radiation and EMP sensors.

Nuclear tests, including underground tests that vent into the atmosphere, produce fallout that not only indicates that a nuclear event has taken place, but, through radiochemical analysis of radionuclides in the fallout, characterize the technology and source of the device. MASINT collection of fallout is most commonly done with airborne dust traps, either on manned aircraft or drones.

Nuclear MASINT (NUCINT)

The information derived from nuclear radiation and other physical phenomena associated with nuclear weapons, reactors, processes, materials, devices, and facilities. Nuclear monitoring can be done remotely or during onsite inspections of nuclear facilities. Data exploitation results in characterization of nuclear weapons, reactors, and materials. A number of systems detect and monitor the world for nuclear explosions, as well as nuclear materials production.

Radiation survey and dosimetry

In nuclear war, after nuclear weapons accidents, and with the contemporary threat of "dirty bomb" radiological warfare, measuring the intensity of high-intensity ionizing radiation, and the cumulative dose received by personnel, is critical safety information < </ref>. While alpha particle emitters such as those in depleted uranium(DU) (i.e., uranium 238) are not a hazard at a distance, alpha particle measurements are necessary for safe handling of projectile dust, or of damaged vehicles with DU armor. The basic field survey instrument is an ionization detector, with various removable shields to permit alpha and beta particles to reach the sensor. However, detectors based on semiconductors, notably hyperpure germanium, have better intrinsic energy resolution than scintillators, and are preferred where feasible for gamma-ray spectrometry. In the case of neutron detectors, high efficiency is gained through the use of scintillating materials rich in hydrogen that scatter neutrons efficiently. Liquid scintillation counters are an efficient and practical means of quantifying beta radiation Specialized instruments are used for tritium survey.

Space-based Nuclear Energy Detection

In 1959, the US started to experiment with space-based nuclear sensors, beginning with the VELA HOTEL satellites. These were originally intended to detect nuclear explosions in space, using X-ray, neutron and gamma-ray detectors. Advanced VELA satellites added devices called bhangmeters, which could detect nuclear tests on earth by detecting a characteristic signature of nuclear bursts: a double light flash, with the flashes milliseconds apart. These satellites also could detect electromagnetic pulse (EMP) signatures from events on Earth.

Several more advanced satellites replaced the early VELAs, and the function exists today as the Integrated Operational Nuclear Detection System (IONDS), as an additional function on the MILSTAR satellites used for GPS navigation information.

Geophysical intelligence

Geophysical intelligence is a branch of MASINT that involves phenomena transmitted through the earth (ground, water, atmosphere) and manmade structures including emitted or reflected sounds, pressure waves, vibrations, and magnetic field or ionosphere disturbances." (FM2-0Ch9)

Acoustic Intelligence

This includes the collection of passive or active emitted or reflected sounds, pressure waves or vibrations in the atmosphere (ACOUSTINT) or in the water (ACINT). (FM2-0Ch9) Hydrophones and sonar, in antisubmarine warfare, are well known, but less well known is the often clandestine process of measuring the signatures of other countries' ships and submarines. It is even possible to use passive sonar to detect aircraft flying low over the sea.

Artillery Ranging

One of the first applications of acoustic and optical MASINT was locating enemy artillery by the sound and flash of their firing, a technique pioneered by Canadian Forces under Gen. Arthur Currie, with AGL Andy McNaughton in a key staff role. The combination of sound ranging (i.e., acoustic MASINT) and flash ranging (i.e., pre-electronic optical ranging) gave information unprecedented for the time, in both accuracy and timeliness. Enemy gun positions were located within 25 to 100 yards, with the information coming in three minutes or less. Today's latest counterbattery radars can give the position within 15-30 seconds. The Canadian units still had a lack of knowledge of wind, temperature, and barometric pressure on the trajectory to the German artillery.

Artillery sound and flash ranging remained in use through WWII and into the postwar years, until mobile counterbattery radar, itself a MASINT radar sensor, became available. These techniques anticipated, and then paralleled, radio direction finding in SIGINT.

Hydrophones

Passive hydrophones, both on ships and airdropped sonobuoys, are used extensively in antisubmarine warfare. The US installed massive SOSUS hydrophone arrays on the ocean floor, to track Soviet and other submarines. Later, "tuna boat" sensing vessels used longer, more sensitive towed passive acoustic arrays than could be deployed from maneuvering vessels, such as submarines and destroyers.

US submarines made extensive clandestine patrols to measure the signatures of Soviet submarines and surface vessels. This acoustic MASINT mission included both routine patrols of attack submarines, and submarines sent to capture the signature of a specific vessel. US antisubmarine technicians on air, surface, and subsurface platforms had extensive libraries of vessel acoustic signatures.

Vietnam-era acoustic MASINT sensors included " Acoubuoy (36 inches long, 26 pounds) floated down by camouflaged parachute and caught in the trees, where it hung to listen. The Spikebuoy (66 inches long, 40 pounds) planted itself in the ground like a lawn dart. Only the antenna, which looked like the stalks of weeds, was left showing above ground." (IglooWhite)

Sonar

Combatant vessels, of course, made extensive use of active sonar, which is yet another acoustic MASINT sensor.

Acoustic sensing of large explosions

An assortment of time-synchronized sensors can characterize conventional or nuclear explosions. One pilot study, the Active Radio Interferometer for Explosion Surveillance (ARIES). This technique implements an operational system for monitoring ionospheric pressure waves resulting from surface or atmospheric nuclear or chemical explosives. Explosions produce pressure waves that can be detected by measuring phase variations between signals generated by ground stations along two different paths to a satellite (Ives & pp. 7-8)

As can many sensors, ARIES can be used for additional purposes. Collaborations are being pursued with the Space Forecast Center to use ARIES data for total electron content measures on a global scale, and with the meteorology/global environment community to monitor global climate change (via tropospheric water vapor content measurements), and by the general ionospheric physics community to study travelling ionospheric disturbances .

Sensors relatively close to a nuclear event, or a high-explosive test simulating a nuclear event, can detect, using acoustic methods, the pressure produced by the blast. These include infrasound microbarographs (acoustic pressure sensors) that detect very low-frequency sound waves in the atmosphere produced by natural and man-made events.

Closely related to the microbarographs, but detecting pressure waves in water, are hydro-acoustic sensors, both underwater microphones and specialized seismic sensors that detect the motion of islands.

Seismic Intelligence

(US Army Field Manual 2-0) defines seismic intelligence as "The passive collection and measurement of seismic waves or vibrations in the earth surface." One strategic application of seismic intelligence makes use of the science of seismology to locate and characterize nuclear testing, especially underground testing. Seismic sensors also can characterize large conventional explosions that are used in testing the high-explosive components of nuclear weapons. Seismic intelligence also can help locate such things as large underground construction projects.

For nuclear test detection, seismic intelligence is limited by the "threshold principle" coined in 1960 by George Kistiakowsky, which recognized that while detection technology would continue to improve, there would be a threshold below which small explosions could not be detected. .

The most common sensor in the Vietnam-era "McNamara Line" of remote sensors was the ADSID (Air-Delivered Seismic Intrusion Detector) sensed earth motion to detect people and vehicles. It resembled the Spikebuoy, except it was smaller and lighter (31 inches long, 25 pounds). The challenge for the seismic sensors (and for the analysts) was not so much in detecting the people and the trucks as it was in separating out the false alarms generated by wind, thunder, rain, earth tremors, and animals—especially frogs." (IglooWhite)

Magnetic MASINT

Magnetic anomaly detection has been widely used in antisubmarine warfare, but it has short range and requires the aircraft to fly at low altitude. In general, it is used for final localization of a submerged submarine before dropping a homing torpedo. There is controversy if, with increasingly intelligent torpedoes and acoustic processing, if MAD is still valuable. The Remotely Emplaced Battlefield Surveillance System (REMBASS) is a US Army program for detecting the presence, speed, and direction of a ferrous object, such as a tank. Coupled with acoustic sensors that recognize the sound signature of a tank, it could offer high accuracy. It also collects weather information .

Radiofrequency MASINT

Where COMINT and ELINT focus on the intentionally transmitted part of the signal, MASINT focuses on unintentionally transmitted information. For example, a given radar antenna will have sidelobes emanating from other than the direction in which the main antenna is aimed. The RADINT (radar intelligence) discipline involves learning to recognize a radar both by its primary signal, captured by ELINT, and its sidelobes, perhaps captured by the main ELINT sensor, or, more likely, a sensor aimed at the sides of the radio antenna.

MASINT associated with COMINT might involve the detection of common background sounds expected with human voice communications. For example, if a given radio signal comes from a radio used in a tank, if the interceptor does not hear engine noise or higher voice frequency than the voice modulation usually uses, even thought the voice conversation is meaningful, MASINT might suggest it is a deception, not coming from a real tank.

Frequency Domain MASINT

Different from emitter location in SIGINT, frequency analysis MASINT concentrates not on finding a specific device, but on characterizing the signatures of a class of devices, based on their intentional and unintentional radio emissions. Devices being characterized could include radars, communication radios, radio signals from foreign remote sensors, radio frequency weapons (RFW), collateral signals from other weapons, weapon precursors, or weapon simulators (for example, electromagnetic pulse signals associated with nuclear bursts); and spurious or unintentional signals.(FM2-0Ch9)

See HF/DF for a discussion of SIGINT-captured information with a MASINT flavor, such as determining the frequency to which a receiver is tuned, from detecting the frequency of the beat frequency oscillator of the superheterodyne receiver.

Electromagnetic Pulse MASINT

Nuclear and large conventional explosions produce radio frequency energy. The characteristics of the EMP will vary with altitude and burst size. EMP-like effects are not always from open-air or space explosions; there has been work with controlled explosions for generating electrical pulse to drive lasers and railgums.

Unintentional Radiation (RINT) MASINT

The integration and specialized application of MASINT techniques against unintentional radiation sources that are incidental to the RF propagation and operating characteristics of military and civil engines, power sources, weapons systems, electronic systems, machinery, equipment, or instruments. These techniques may be valuable in detecting, tracking, and monitoring a variety of activities of interest.(FM2-0Ch9)

A Vietnam-era "Black Crow" RINT sensor, carried aboard AC-130 gunships, detected the "static" produced by the ignition system of trucks on the Ho Chi Minh trail, from distances up to 10 miles .

This discipline blurs into the various techniques for collecting COMINT from unintentional radiation, both electromagnetic and acoustic, from electronic devices. TEMPEST is an unclassified US code word for the set of techniques for securing equipment from eavesdropping on Van Eck radiation and other emanations.

External links

• http://www.gpo.gov/congress/house/intel/ic21/ic21007.html