Electronic Espionage Detection and Prevention

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Physical Search Efforts

The third part of a sweep is a physical inspection or search of the area.  The object of the inspection is to find eavesdropping devices that the telephone testing and RF sweep will not find.  Typical devices that can only be found by a visual inspection are:

• Tape recorders and other audio recording devices including minidisk recorders and digital voice loggers

• Hard-wired microphones

• Loudspeakers used for paging and fire alarm voice annunciation that are inactive during normal times.  These can be utilized as microphones with minimal modification

• Dormant, inactive, or failed RF transmitters

• Timer controlled RF transmitters

• Remotely controlled transmitters

• Covert video cameras

• Contact and Spike microphones

• Audio paths to other areas-  through floors, ceilings, and walls

• Vulnerability of the area to external listening devices including the fabled laser listening systems.

Physical search techniques include visual inspection of all of the furnishings in the area.  Ceiling areas are inspected.  We also search the areas adjoining the offices being swept looking for contact and spike microphones as well as audio leakage paths. 

The picture below shows two miniature microphones used in hard-wired audio surveillance devices.  In  normal life they are used in hearing aids, but they are used with great success in surveillance installations.  Some are a bit larger and some are even tinier.  Imagine trying to find one of these in an office.  You have to rely on trained, skilled personnel with the right equipment to be able to be sure an area is clean.  Simple detection equipment won't find it and untrained sweepers won't recognize the methods of installation or the symptoms.  Click on the picture for other miniature microphone photos.

To make the search thorough and exacting we use a variety of equipment.  Some are highlighted below:

Video Inspection Tool We use this to see into inaccessible places where listening devices can be hidden.   Places include HVAC ducts, under file drawers, in radiators and air terminal units, in ceilings and inaccessible air return plenums.

Our camera is equipped with IR LEDs to provide light in dark areas.

Because it is sensitive in IR wavelengths, our camera also will detect infrared transmitters operating in the area.

Nonlinear Junction Detector

Nonlinear Junction Detectors are used to detect and locate electronic devices.  They use a radio frequency technique to indicate the presence of transistors, diodes, and integrated circuits.  We use the most powerful and sensitive junction detectors available in the US.

Audio Amplifier

We use a high gain audio amplifier to test for a number of vulnerabilities.  With it we test speakers for their ability to act as microphones.   Low voltage wiring is tested for audio from the area being swept.  With its contact microphone, we can test wall surfaces, plumbing and HVAC installations for the ability to pass audio.  The amplifier can also power devices that are attached to the wiring being tested, aiding in their rapid detection.

Thermal Imager

We use infrared thermal imaging to aid in the detection of hidden devices.  The thermal imager reveals the tiny amounts of heat radiated by many types of eavesdropping devices.  Click on the picture for more information.

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Last modified: March 23, 2006