Surveillance Counter Measures
" Bug Sweeps "
832-2388 for Service
A 'bug' is the common name for a covert
listening device, usually a combination of a miniature
radio transmitter with a microphone. The use of bugs,
called bugging, is a common technique in espionage and,
increasingly, in police investigations.
Most bugs use a radio transmitter, but there are many
other options for carrying a signal: radio frequencies
may be sent through the main wiring of a building and
picked up outside; transmissions from a cordless phone
can be monitored; and it is possible to pick up the data
from poorly configured wireless computer networks or
tune in to the radio emissions of a computer
Bugs come in all shapes and sizes. The original
purpose of bugs was to relay sound, but today the
miniaturisation of electronics has progressed so far
that even commercially-available bugs designed to carry
TV signals are usually the size of a cigarette packet.
Professional bugs can fit into pens, calculators and
other commonplace items. Some are only the size of small
shirt buttons, although the power and operational life
of the smallest bugs is very short.
The development of modern 'wireless' technology has
presented new security concerns. To be 'wireless' a
device must transmit information, either by radio waves
or infrared light, and this potentially makes all the
information sent via that link available to others.
Radio waves are the easiest to intercept, but even
infrared transmissions can be picked up through a
window. Some wireless devices, such as wireless computer
networks, do encrypt transmissions, but the standard
forms of encryption are weak. Such devices, whether
wireless keyboards or wireless telephones, should not be
used in any environment where sensitive information is
Most bugs emit radio waves. The standard
counter-measure for bugs is therefore to 'sweep' for
them with a receiver, looking for the radio emissions.
Professional sweeping devices are very expensive.
Low-tech sweeping devices are available through amateur
electrical magazines, or they may be built from circuit
designs on the Internet. But sweeping is not foolproof.
Advanced bugs can be remotely operated to switch on and
off, and some even rapidly switch frequencies according
to a predetermined pattern in order to make location
with sweepers more difficult. A bug that has run out of
power may not show up during a sweep, which means that
the sweeper will not be alerted to the surveillance.
Those bugs that do not emit radio waves are very
difficult to detect. Radio-based bugs are a technical
solution to a problem - remotely listening to people's
conversations - but a simpler option is simply to record
the conversation on a normal recording machine. There
are a number of options for this:
Pocket sized devices, either worn or carried in
baggage, linked to a small microphone which is usually
mounted on the surface to pick up the audio. Digital
devices such as minidisc recorders or the latest
palm-sized camcorders produce very high quality
recordings and are conveniently small.
recording devices hidden in the room, for example above
suspended ceilings. These are popular in workplaces for
Ultra-directional microphones, or
parabolic microphones. These are like the microphones
seen on camcorders, or carried by sound technicians.
They are constructed to receive signals only from one
direction. The most high-tech directional microphones
can eavesdrop on conversations from a hundred metres
away or more. Microphone arrays can be used as well.
Laser microphones. These are very expensive and
highly technical to operate. A laser beam is bounced off
a window, or off any object near to the conversation
monitored. Any object which can resonate/vibrate (for
example, a picture on a wall) will do so in response to
the pressure waves created by noises present in a room.
The electronics detect the minute difference in the
distance travelled by the light to pick up this
resonance and reproduce the sound causing it.
equipment that is not a threat on itself may exhibit
Mobile phones can be used as bugs as
The adversary can use a trojan horse to
acquire access to microphones connected to computers.
If a microphone is hidden in a room it is almost
impossible to detect, as it has no radio emission. Very
sensitive equipment could be used to look for magnetic
fields, or for the characteristic electrical 'noise'
emitted by the computerised technology in digital tape
recorders; however, if the place being monitored has
many computers, photocopiers or other pieces of
electrical equipment installed, it may become very
difficult. Older analog equipment is even more difficult
Another method is using very sensitive infrared
cameras to detect waste heat of a bug, or different
thermal conductivity of a place where it is hidden after
briefly chilling the surface of the object with eg.
liquid nitrogen. -H
If you need a profeesional to sweep your office or
home please call (714) 773-5345 or (877) 832-2388.
We at Gailey Associates, Inc. are Licensed Private
Investigators and can help you with a TSCM. Please call