To: TSCM-L@yahoogroups.com
From: "James M. Atkinson"
Subject: Re: [TSCM-L] Re: "through-the-wall audio surveillance system"


The patent is nothing special, and this "special" method of 
eavesdropping has been around for a number of years, and certainly 
before the early to mid 70's.

In fact the 2010A Doppler Stethoscope made by Marty Kaiser was an 
excellent example of this, and you could retrieve extremely clear 
audio by using it and bouncing the 10 GHz signal off the metallic 
content of a certificate or even a piece of paper hanging on the 
wall. The key was to find something in the room that with light 
enough to move with room vibration such as curtains, paper, pictures, 
etc, and then to "illuminate" it with  signal that had a wavelength 
that was six times or more the thickness of the thing that was moving.

In practical usage a diploma, or certificate hanging on an executives 
wall could be turned into an excellent eavesdropping device, so could 
a few sheet of paper left laying on a table... anything that was 
light enough to move or vibrate with room air. A glass vase with a 
thin wall also works, and does lamps and other fixtures that are not 
a heavy solid mass.

A low frequency can be used, but you will start developing less than 
desirable results with low frequencies, but will receive better 
results with frequencies even higher that 10 GHz. Above 33 GHz you 
can actually start using the water in the air as the microphone, and 
you will have profound success with doing this when you get over 50-60 GHz.

At 10 GHz you only need a few mW of power to do this successfully 
from a few feet away, and 100 mW can get an eavesdropper a fairly 
respectable distance from the target. Some police radar guns will 
also let you do this with with  minor mod where you simply point the 
radar gun and use it like a highly directional microphone that can 
shoot through walls. Prison escape teams have been using these for 
years to listen for escapees in the woods, or hiding in corn fields 
without actually entering the woods.

One of the more humorous eavesdropping vulnerabilities on Embassy Row 
in Washington, DC are the X-Band alarm sensors all the Embassies 
install in their more sensitive rooms, but which they neglect to turn 
off during sensitive/classified discussions their diplomats are 
having. An eavesdropping can simply tune in the frequency of the 
X-Band (or K-Band) alarm sensor and listen in to classified 
discussions. Even when they turn these sensors off during meetings, 
there is still enough loose items on the walls to provide a wealth of 
vibrating surfaces that a microwave signal can bounce off of.

With this is mind the TSCM specialist needs to always search for any 
signal with could be a source of illumination, and pay extremely 
close attention to any signal present in the area being inspected, 
but which may of may not be originating within the area being 
inspected, but which may provide a reflection of an external signal 
above a dangerous threshold. An example of this is building D of the 
Georgetown University Hospital complex which is only a short distance 
South of a diplomatic facility.  Merely being near and above a nearby 
diplomatic facility isn't the biggest problem by itself, but because 
this diplomatic location is saturated with RF energy between 10 and 
15 GHz it becomes extraordinarily easy for an eavesdropper to listen 
in to diplomats talking about classified matters. While the GUMC is 
not the optimal location for a listening post the mechanical room on 
the roof provides a cozy place for diplomatic mischief of an 
electronic variety. Let's not even talk about the "special species of 
trees" that grow in the parkway to the North of the facility, or the 
rather large "burrowing creatures" just to the east.

Don't start getting spun up about acoustic masking either, because it 
is not going to be of much value as it is generally only effective 
against solid masses of building materials, and not light weight 
pieces of paper of metal hung on a wall. Transducers mounted on glass 
may make the glass in the window vibrate, but it is not going to do 
much to that photograph which is mounted on the wall on the other 
side of the room.

The higher the frequency used for illumination the more dangerous 
this situation becomes, and when the eavesdropper can gain the high 
ground near the target he owns the facility on which he is running 
the technical surveillance. Frequencies used for local non-hostile 
microwave communications and satellite uplinks can be exploited as 
the illumination signal, so all the eavesdropper has to do is focus 
one antenna on the source of the illumination signal, and a second on 
the target, and then dial-up a delay and phase correction.

If you want to hear an earful of classified information leaking out 
of the Chancery, then spend some time on the roof of building D at 
GUMC with your dish pointed a little to the North to hear about the 
which wine goes best with fish between discussions on diplomatic 
manuvering. ;-)

-jma