Eavesdropping and Counter-Measures: Technology and Techniques
You need to know how to protect yourself, since your security department or
any consultant may not be truly aware of these threats and therefore not
dependable. Since September 11th, a number of businesses entered the security field with little to no knowledge of the trade itself; only of its profit potential. Even outfits that have been around for some time and well-established have not been able to stay current with the latest innovations.
Realistically, viewing your threat level has to be considered since everyone
should expect some sort of impending privacy issue no matter how small. Thanks
largely to the Internet you can arm yourself with much of the knowledge and
equipment that the so-called experts use. If a respected agent of computer crimes
for the Secret Service in NYC had his T-Mobile Sidekick hacked, who knows what else
happens out there to others in any business.
We’ll start acoustic ducting evaluation is the inspection of air ducts, baseboard
heaters, coffee rooms, lounges, bathrooms or any way the architecture of a building
can transfer sound. A simple example is to put your ear to a wall and listen.
Basically anything that requires the use of the naked ear is called an acoustic
bug. Softer surfaces can help muffle sounds but there are more efficient means out
there. So be aware that the way an office site is designed can act as a conduit for
conversations. Also, be aware of any changes can have adverse affects. Simply
playing music can do wonders for masking conversations.
Inspection of telephone equipment and wiring is called line analysis. This is
trickier than it seems since sometimes a possible weakness has an actual purpose to
the telecommunication system. Especially if it requires constant maintenance and
All instruments should be opened and inspected. Ideally they should be
compared with a known safe phone or device. If you’re not sure, just remove that
piece of loose components and wiring and see if the phone still works. The wiring
can be modified in a switch within the handset that essentially turns it into a
microphone. If you bypass this hook switch, you can listen in from anywhere on the
equipment won’t be able to detect this. Time Domain Reflectometry is the sending
of a pulse down a telephone line. If there is some sort of disruption; a wall outlet or
wiretap; a portion of the pulse will be
sent back to the device called a Time Domain Reflectometer (TDR). Then the time
difference between the reflection and the continuous run is measured. This helps in
determining the distance to the anomaly.
These devices can perform all sorts of diagnostics including mapping a wire
network. That can be useful in locating a hidden phone. Hidden phones have several
obvious uses such as making long distance phone calls to being placed in an office
across the street to receive betting requests by bookies; a practice called back
strapping. If you open up the modular jacks where you connect your phone, you’ll
usually see four wires. In most cases only two wires are connected; commonly
known as ring and tip. If you see all four connected, be aware that is not usually
consistent for most wiring situations, especially in homes. The other two wires
could be used for a bugging device.
For instance, the microphone you use in a voice recorder can be cut in half.
Connect the mike head to one set of unused wires anywhere on the phone wire.
Then, so long as there are no breaks in the wire, connect the other end to the jack
that connects to your recorder. Now place your recorder to be VOX (voice) activated
and now you have an extremely reliable bug. By the way, this should be manually
inspected for since using a specialized bug detector may see nothing wrong or
inconsistent. A bug such as this that connects to a wire is called a direct tap.
The other general type is called an inductive tap. This is when an instrument is
outside a wire but can still distinguish what’s transacting over a wire. They are
harder to detect since they don’t draw power from the line such a standard
telephone would. These are referred to as snuffle bugs. A simple probe used in
hunting wire signals has a speaker, which can display sounds. By
accident one day I was working on an apartment intercom system while using a
probe. I could hear conversations throughout the building quite clearly just
through the intercom boxes mounted on walls from the master unit in the
If you’re using wireless headsets or cordless phones, the radio signals can be
intercepted. A cordless phone acts like a radio, but depending on the frequency and
a few other factors, can make interception extremely difficult. With some
manufacturers, you can buy the same model as your neighbors or the office and
have it join their phone system. Double check Caller ID boxes to see if they also
record numbers dialed besides obviously those being received. If you’re using VOIP
(Voice Over IP), remember that calls can be recorded in a fashion identical to
intercepting data between two computers.
These packets of data can reassemble an audio file. Obviously electronic
devices possess semiconductor components such as diodes, resistors and such. The
method to hunt for these components is called Non-Linear Junction Detection
(NLJD). The NLJD unit emits a radio signal while listening for the return signal from
an electronic device. This becomes very useful when a bug is embedded in a picture
frame or wall. The eavesdropping device doesn’t have to be active for it to be
discovered. If a device is active and transmitting wirelessly (or even on a wire), you
can detect it with a Radio Frequency Spectrum Analyzer. Depending on the detection
device used, you can determine whether voice, data or video is being sent, and
possibly listen to the data. Try to use different size antennas or buy one that
collapses. Different frequencies can be detected more efficiently by using various
sizes. The use of filters with antennas can also help pinpoint devices on specific
Electronics such as computers, FAX machines and especially CRT monitors can
radiate electromagnetic signals or pulses that can be received by other equipment.
This is known TEMPEST. One way to complicate the surveillance of this is to use
certain fonts and line walls or equipment with different gauges of copper mesh wire.
You can further enhance this posture by using special paints, which block radio
Radio waves will look for a leak or break, so be careful of defensive
applications. One-way window tints can help in blocking signals. Since an
electronic device could generate some heat they can be detected in another way.
The use of a thermal imagery device can detect and actually see minute amounts of
heat radiated for your viewing. You can hide the heat signatures by using creams or
neoprene. Technology exists to collect information from blinking LEDs of modems,
routers, print servers and similar devices. You can only see some general blinking
but with the use of properly tuned optics, filters, oscilloscopes and good timing you
can discern much more. One of the LEDs on your keyboard can be altered to blink
while you are typing in a fashion similar to Morse Code. You can also use a tap in
the keyboard that sends out radio waves again similar to Morse Code and no anti-
virus software will ever be able to find it. Even when a CRT computer monitor is
facing a wall the light can be in a sense read by its flickering emanations from some
distance. A good defensive measure is to buy new LCD flat panel types.
Another approach to attacking FAX machines is to simply record the noises it
makes and play it back to another machine. I used to do this for a client so they
could keep a record of all the faxes they made and received. There are creative and
potentially illegal defenses against wiretappers and Peeping Toms. One is to
transmit an extremely high pitch down the wire, thereby rupturing the listener’s
eardrums. I knew someone who once sent a powerful electrical spike down his
phone wire thereby destroying his divorced wife’s recorder.
By the way, this leads to another topic-expect the device to be discovered
someday. Don’t leave your fingerprints on it. He found it and had it dusted, thereby
producing some prints. My friend used this as leverage against the Private
Investigator that planted it. Advice to Private Investigators, a word to the wise: if you
do this part-time, hire someone who does this full-time. This P.I. lost his license
and almost went to jail. The lawyer who recommended him got into a lot of trouble
as well. He received some unwanted attention from the Feds because of his
telephone dealings went across state lines and also happened to involve the Post
There is another budding field related to this topic called Protective
Intelligence. Currently there are only a few experts who do this kind of work.
A laser or an infrared beam can be used at a considerable distance from a
target building. Conversational sounds can vibrate unto solid objects such as
windows. The beam’s reflection varies in relation to the movement to the window,
which is received and converted back into something audible. To mask the sounds,
you could attach a vibrating device (basically an altered electric razor) to the
Of course if the window is open, then a laser can target another object instead
of the window. A beam of light or laser can be directed to go through a window
onto a solid object thereby nullifying such defensive measures again. Generally you
really can’t detect such attacks unless the laser, infrared or light beam is being used
that moment. Certain materials can be used to detect IR emissions, as well as the
use of passive night vision gear. Certain fabrics or even a curtain may actually show
the spot where a beam of light or laser is being focused. Unless the room is dusty or
you have an artificial can smoke, you can follow the beam up to a point and
guesstimate it’s location. One type of optical bug is an infrared transmitter. When
placed in the area of interest for transmission of the conversation to an infrared
receiver which will then translate the conversation into an audible format.
Many of these same procedures used can be applied to locating hidden
cameras. A relatively new device uses a series of lasers to seek out optics. This was
originally intended to locate snipers by bodyguards.
I have listed the techniques, counter-measures and then the counter to the
counter-measures to prevent any false sense of security. Usually constant vigilance
is your best weapon besides knowing what to look for. Even if you find a “bug
sweeper” with good credentials, certifications and experience, ask them detailed
questions. Not just to test them but also for your own peace-of-mind. This makes
our job easier and we appreciate greatly when dealing with knowledgeable