Re: TEMPEST Question

[Doug.Brightwell@Corp.Sun.COM (Doug Brightwell)]

	>> Cpu signal is the easiest to detect, but not the only
	>> one.  Other possible sources of emissions are all
	>> kinds of communications cables.  Unshielded RS-232 to
	>> the modem, possibly even the connections to the disk
	>> drives.

Synching up to monitor signals, I can understand.

But as a non-technical person, what I'm struggling to understand is how
a surveillance team could monitor the emmisions from such cables and
have any clue as to what they are. Let's say they zeroed in on my
poorly shielded modem cable and were able to tune into a stream of 0's
and 1's. How could they then resolve that digital data into anything
meaningful? It could be one of any number of documents created by one
of any number of programs on one of any number of platforms. How do the
spies know they're dealing with a Frame page layout document created on
a Sun workstation versus a spreadsheet created on a Mac?

Even if it's just a plain text file how could the surveillance team
read it? Does each member of the ASCII character set have specific and
identifiable radiation signatures? For example, does the letter "k" as
it passes through my modem cable have a characteristic EMR that is the
same for all machines?

Sorry if this query is too basic, but I would appreciate any enlightenment...

Doug