In comp.sys.ibm.pc.hardware.storage Jamie t wrote:
Arno Wagner wrote:

In comp.sys.ibm.pc.hardware.storage Joey wrote:

Suppose someone visited your office or home and tried to make a voice
recording using a hidden recorder.


If they used a older-style dictation machine based on tape then you
could detect the electromagnetic transmissions from the dictation
machine when it was recording.


But how would you detect if someone was secretly recording with an MP3
player that recorded to flash memory?


Is there some transmission which could be detected?
Perhaps some low power ultra high frequency from chip refresh cycles?


Not really. You could maybe detect that it was turned on with
an RF scanner. But if it is low power enough (most MP3 players
are, since they are optimised for that) and well shielded, you
would likely get nothing in today's RF polluted environment.
In addition the attacker may just add some more shielding to be
sure. I think you can basically forget about this, unless you
can take the devices away from people.

Arno

i have seen a device used by an electrical instructor at a trade
school. he does not like any Cell, recorders or electronic devices
active while in his class. this device will buzz and vibrate in his
pocket as he walks around the class, he can walk right up to the
student that has something on.. it works by detecting a variation
of known R.F. frequencies that helps him decide on an LCD screen of
the device what it could be, and then it has wide band detection of
any R.F. generation.. as you know, most devices do generate some
R.F. of some freq.. i've seen it in use and its on the
market... all i can say is by his words, "it works very good"

That sounds like BS to me. Of course cellphones are very easy to
detect that way, and I expect that is what he is showing off. Forget
about non-woreless devices. They have several orders of magnitude
less RF emanations. This guy is likely demonstrating with
cellphones and then claiming he can detect the other things
without ever demonstrating.

Arno