From: "Cynthia H. Brown" <cynthb@sonetis.com>
Date: Wed, 12 Mar 1997 08:43:30 -0800 (PST)
To: Dale Thorn <dthorn@gte.net>
Subject: Re: TEMPEST protection
In-Reply-To: <33265C33.15BB@gte.net>
Message-ID: <Pine.BSD/.3.91.970312113344.21996D-100000@mrburns.iosphere.net>
MIME-Version: 1.0
Content-Type: text/plain


<sorry for the earlier finger glitch>

On Tue, 11 Mar 1997, Dale Thorn wrote:

> Actually, the computer you type on will be very easy to pick out
> of the noise field with modest spy equipment sitting down the street.
> 
> There's a company (I lost the brochure) who sell EM attenuator
> material, some preconfigured, and presumably some bulk.  It should
> be easy to find on the Web.  Once you get some really dramatic
> attenuation, particularly of the keyboard (and particularly during
> password confirmations, etc.), you should do your own preliminary
> monitoring with some of those band-sweep gadgets.  Steady noise
> of course is nothing compared to the spikes from some of the keyboard
> outputs...
> 
> Once you've identified all (we can hope, can't we) of the problem
> signals still leaking through the shielding (albeit at greatly
> reduced levels), you can direct different kinds of efforts there,
> including random noise from other computers which use the exact
> same output devices.

>From what I've seen, it's a lot easier for "the bad guys" to concentrate 
on monitor emissions - you can read the screen someone's looking at, and 
not just the key-clicks.  Won't get you blanked-out passwords, though.  
Much of the monitor's emissions may be out the back.

Other places to look for emissions: the power supply, and the connection 
points for peripherals.  Make sure you leave adequate ventilation, though 
(another tricky part).

Cynthia

===============================================================
		   Cynthia H. Brown, P.Eng.
E-mail:     cynthb@iosphere.net  | PGP Key:  See Home Page
Home Page:  http://www.iosphere.net/~cynthb/
Junk mail will be ignored in the order in which it is received.

        Klein bottle for rent; enquire within.