From: Jim choate <ravage@wixer.bga.com>
Date: Wed, 22 Dec 93 07:55:30 PST
To: nowhere@bsu-cs.bsu.edu (Anonymous)
Subject: Re: eavesdropping detection
In-Reply-To: <9312220304.AA20790@bsu-cs.bsu.edu>
Message-ID: <9312221537.AA29903@wixer>
MIME-Version: 1.0
Content-Type: text/plain


>
> 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