From: Ray Arachelian <sunder@brainlink.com>
Date: Sat, 3 May 1997 03:15:45 +0800
To: cypherpunks@toad.com
Subject: Building a Tempest Interceptor (fwd)
Message-ID: <Pine.SUN.3.91.970502144943.29363F-100000@beast.brainlink.com>
MIME-Version: 1.0
Content-Type: text/plain


This was on the Surveillance List...


by Frank Jones
aka SpyKing@thecodex.com
http://www.thecodex.com
Copyright 1997

The is very little public knowledge about TEMPEST. Most infomation, including how to safeguard against monitoring, has been classified by the government.  You can view an article I wrote on TEMPEST at: http://www.thecodex.com/c_tempest.html and another at: http://www.thecodex.com/rise.html

In order to protect computers and CRT's from electromagnetic emission monitoring (interception, recontruction and viewing) it is necessary to use shielding. This shielding is available in several forms but that is another article... 

Once the shielding is installed, how do you test it for leakage? It is necessary to see if you can monitor the device yourself.  Since TEMPEST monitoring equipment is normally very expensive and hard to come by, here 
is a simple way to construct a "simple" monitoring device that will help 
you detemine if your computer can be "snooped" on by outside sources... 
this device was designed for "defensive" purposes and should NOT be used offensively... it does not have the distance capability of my DataScan 
device but it WILL work as a laboratory benchtop demo device...

Like Van Eck and Moller, I have deliberately flawed the article for the technically challenged... After all, we don't want everyone to have one 
of these, do we?

TEMPEST Interceptor - Follow my instructions...

You need to learn something about electronics to make this happen. 
The first lesson will be to construct a sync generator to drive the 
computer monitor without any signal or video. 

To start this you must take your spectrum analyzer, turn off every appliance 
in the area. Put the analyzer near the computer monitor, turn on the monitor but NOT the computer. Start searching around 15Khz. You should get a strong signal somewhere between 14Khz & 17Khz. Log that frequency. Next try looking around 30Hz to 60Hz. Which is stronger 30 or 60?  Log that. 

Next we're gonna build a "computer sync generator"  (video gear will not work). Most technician's who have tried to build a TEMPEST interceptor have been trying to use "off-the-shelf" products. Don't believe what you read or hear, they won't work. You've got to build a computer sync generator. 

It isn't really so hard to do. Get yourself a copy of the "CMOS Cookbook". 
It's around.  In there it shows how to build a 555 timer. It is a small and simple circut. Maybe 5 components. The 555 has in it all the clock and electronics to make a timer from 1Hz to 10Mhz. Follow the instructions and 
make a variable timer (it is really simple).  Make the first one run at the exact frequency of the monitor, say 16 Khz. Next make a seperate one at the second frequency say 30 Hz. Then tie them together with a .o1 Mfd cap. The output should drive your monitor (generator is done).

Two minor things I forgot to mention. The output of the 555 is about 5 to 
12 volts. You will need to attenuate it to about .3 volts. Several resistors will do.

The other thing is that you need a negative pulse out of the 555. The normal output of a 555 is a square wave. On and off . You must vary the duty cycle 
to create a square wave which is most of the time on and the sync duration off.  

You now need a seperate dedicated computer monitor. Open the input plug and find the shielded cable inside. Attach the output of your circut to the 
center-conductor and the battery minus from your circut to the shield. You 
have a solid black screen on the monitor. Turn up the brightness. There should be no rolling and weaving. If so... adjust the pot in YOUR CIRCUIT not the monitor, to stop it.  

Next step. Collect the signal you hear and see on your anaylzer/receiver. 
Take the output of your reciever tuned to those frequencies. Connect the 
output through a .01 mfd cap to the output of the sync generator and "viola" you should start to see the monitors radiated signal on your monitor. 
Shielding your viewing monitor from the recieving monitor and small 
adjustments in your generator frequency should do it. In fact no 
adjustments should still do it. 

The antenna that you use is critical. 
Make sure you use the right one...  ;-)


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