From: Michael Graffam <phundie@mhv.net>
Date: Wed, 18 Mar 1998 10:36:54 -0800 (PST)
To: The Spectre <spectre@anthrax.net>
Subject: Re: EMI, Van Eck, etc.
In-Reply-To: <B0000003809@hades.crmcom.com>
Message-ID: <Pine.LNX.3.96.980318132056.32100A-100000@localhost>
MIME-Version: 1.0
Content-Type: text/plain


On Tue, 17 Mar 1998, The Spectre wrote:
> Does anyone have a document for actually modifying a television set to do
> this sort of thing?  It doesn't have to be extremely long ranged, and could
> in fact be very short range.. I am interested in performing my own
> experiments into defeating this sort of eavesdropping.

Well, for one.. I don't think (speculation, I haven't done any real
investigation into it yet..) that this oft repeated maxim applies to
modern hi-res monitors with super refresh rates. I don't think that a
TV could be used to display emanations from a new monitor. OTOH, I
haven't looked into modern TV technology at all.. I don't know what
the new sets are really capable of. Suffice it to say, you probably
won't be able to modify an older set to snoop on a new monitor set up
at 1280x1024, but if for experiment purposes to just did a text display
you should be able to snoop that with an older set.

> Also, would it be possible to scramble the signal into an unusable level by
> simply putting another device emanating RF at the snooping frequencies
> nearby the machine that you want to protect?  Something generating white
> noise at that frequency, but with a purposely built antenna, say a high
> gain type turned outward from the monitor, with a significantly higher
> power output than the monitor?

I would think that any device of this sort would make the monitor's 
display rather distorted.. unless you put shielding around it to
protect it, but that same shielding would prevent usable EMR.

Find the Unofficial Tempest Homepage (sorry, dont have the URL handy..
but I found it a few times by searching out the title from altavista)
it has links to Van Eck's original paper, and if memory serves papers
that "fill in" the gaps of Van Eck's work to help in modifying
equipment.

Michael J. Graffam (mgraffam@mhv.net)
http://www.mhv.net/~mgraffam -- Philosophy, Religion, Computers, Crypto, etc
"Act only according to that maxim by which you can at the same time will that
it should become a universal law.." - Immanuel Kant "Metaphysics of Morals"

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