eavesdropping detection

How would one go about detecting any suspected eavedropping devices
in one's home in an inexpensive fashion? Sorry about the off-topic
question, but what the heck.

Normally, by a near-field receiver.  I don't know of any other way.

An AM band unit is about $110 and an FM band unit is $200-400.

I've seen ads for the AM band and I saw the FM unit at Hamvention in Dayton.

The AM band unit can detect FM transmissions, you just can't hear the
traffic, it's just quiet.  It was also advertised to be able to detect
leaking microwaves, etc.

If I understand it, nearfield receivers and frequency counters rely on
the relative strength surrounding a transmitter at close range to sync
with the frequency.  No tuning at all.

> How would one go about detecting any suspected eavedropping devices
> in one's home in an inexpensive fashion? Sorry about the off-topic
> question, but what the heck.


sdw
-- 
Stephen D. Williams  Local Internet Gateway Co.; SDW Systems 513 496-5223APager
LIG dev./sales       Internet: sdw@lig.net CIS 76244.210@compuserve.com
OO R&D Source Dist.  By Horse: 2464 Rosina Dr., Miamisburg, OH 45342-6430
GNU Support          ICBM: 39 34N 85 15W I love it when a plan comes together

>
> How would one go about detecting any suspected eavedropping devices
> in one's home in an inexpensive fashion? Sorry about the off-topic
> question, but what the heck.
>

Hi,

One of the first things that I would look for would be a spectrum analyzer of
fairly wide bandwidth. I would then create a audio 'popper', a device which
make very precise clicks. I would set this loose in the area I wished to
sweep and then look at the spectrum analyzer for corresponding pulses of rf.
The majority of modern listening devices use a VOX circuit to save batteries
and make the bug harder to detect. If you can't find a spectrum analyzer then
go for a grid dip meter. This is a tuned circuit which has various plug-in
coils to change its frequency of detection. The problem here is sensitivity
(you will have to get close to the transmitter) and ease of use (you are
going to drag lots of coils around).

For physical phone taps from your network interface (the phone companies box
on the wall outside your building) you have to do some preliminary work. To
check for taps inside your house you need to get a Time Domain Reflectometer
and connect it to the NI and then look at your cables. You need to record
this in some manner and store it for future reference (you need to do this
each time you change phones or otherwise alter the layout). If there is a
change in the wiring the TDR signal will be significantly different. This
should even detect induction style pickups so long as they are inside the
building.

As to the telephone switch itself, short of hacking ma bell I don't know of a
feasible way to detect them.

For spike microphones and such there are two methods of defense, easy and
hard. The easy way is to set of some kind of noise generator to mask the
sounds and do a physical search of the outside of the building w/ a linemans
induction pickup. If the mike's are using cable (not rf or you would have
found them w/ the spectrum analyzer) then you should hear the signal at some
point. The hard way (assuming they are sending the signal in some other way
other than rf or land line, say a pwm laser) is to get yourself a set of IR
goggles and check the place out.

Hope this helps....

Have a Merry Christmas

...
> For spike microphones and such there are two methods of defense, easy and
> hard. The easy way is to set of some kind of noise generator to mask the
> sounds and do a physical search of the outside of the building w/ a linemans
> induction pickup. If the mike's are using cable (not rf or you would have
> found them w/ the spectrum analyzer) then you should hear the signal at some
> point. The hard way (assuming they are sending the signal in some other way
> other than rf or land line, say a pwm laser) is to get yourself a set of IR
> goggles and check the place out.

Most camcorders can see IR normally and have an IR filter that sometimes
can be removed.  Turning off the lights will help.

> Hope this helps....
> 
> Have a Merry Christmas
> 

sdw
-- 
Stephen D. Williams  Local Internet Gateway Co.; SDW Systems 513 496-5223APager
LIG dev./sales       Internet: sdw@lig.net CIS 76244.210@compuserve.com
OO R&D Source Dist.  By Horse: 2464 Rosina Dr., Miamisburg, OH 45342-6430
GNU Support          ICBM: 39 34N 85 15W I love it when a plan comes together

Yeah, you are correct that some cameras (especially the ones w/ CCD's) can
see IR. However they are not tuned to the lower end of the IR band as normal
IR goggles (at least the Russian tank driver pair that I have access to) and
it is possible to use a laser designator style setup (toward the lower IR end)
to defeat a normal video camera. As to turning the light off, unless you are
dealing with a complete incompetant they will bounce it off a window or a
spike reflector through a wall or roof. Another very good place to check for
these style bugs is in fireplaces.