spyproofing your house/work building

Arsen Ray Arachelian rarachel at prism.poly.edu
Fri Mar 18 11:28:37 PST 1994

> Or you could just put a nice incandescent light fixture between you and the
> drapes; nice IR output from those bulbs. Halogen fixtures ought to work
> also, but fluorescent bulbs don't produce enough IR.

Might not work as the incandescent light source still won't stop the
window from vibrating.  They can still reflect a laser off it regardless
of the output of another source.  They may have tweak their amps... but
it won't help against it.
> More importantly: attach a contact-speaker to each pane of glass, and feed
> Top 40 radio to it. There have been reported cases of spy types bouncing
> laser beams off windows and using the reflected beams to reproduce the
> vibrations produced in the glass by reflected sound; in other words, the
> window panes are large membranes which vibrate in sync with the sound that
> hits them, so you want to override those vibrations with something else.

Won't work.  You need a random, independant source of noise.  Each
window pane should have its own noise source attached to a speaker.
If the speaker is tuned into a radio station, they too can tune into
the same station, then substract the two signals giving them a fairly
clear ear to listen in from.  A random noise source that is independant
will do well because they can't substract it out.  If two windows in
two different rooms also use the same random noise, they can differentiate
between the two rooms and get the sound.

I suppose they could bounce four or five lasers on the same window in
hopes of being able to use two beams for the substraction, but if the
speaker is placed in a good location, or several of them are placed
on the same window, they'll have a bitch of a time getting anything.

In that case they'll probably resort to using microwaves to bounce off
a metal item in the room which would also vibrate with any sounds in the
room.  The only real defense against that would be strong shielding
and a microwave detector to see if the shielding failed... the shielding
has to be sound isolated or else the walls of the shielding could be
used to get sound.. :-(  Pretty nasty shit, eh?
> This reeks of paranoia, eh

Nope, it's da truth. :-)  I'm not doing this out of paranoia.  I'm
learning about this incase the police state comes anytime soon.  It's
far better to learn about it before than after it's too late. 


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