Readers' Letters Storm in a TEMPEST?

And why would we want to look at your PC, anyway?

Can't pay - won't pay

To quote from your page on Only UK viewers have to pay:-

"instead they work by detecting the TV tuner's local oscillator which always leaks a small amount of
radiation back up the aerial."

I have to question this because there's a couple of flaws here. Firstly 99% of tv's sold now conform to CE approval, hence limiting there RF emissions. And secondly, what happens if your using a cable tv /
satellite tuner / etc?? The local oscillator is going to not be passed up the coax to the antenna because of a cascade of RF amplifiers in those devices. I suppose the tv licensing 'authority' will try to kid us that the signal goes through the satellite tuner and out of the dish to the satellite where they can use XY or Z to pinpoint the BBC service thief?!

'The' TV detector van should be renamed "psychological prompting vehicle" because that's the only purpose it serves, ie, The one and only psychological prompting vehicle is seen in the area and people spread the word, and lo and behold, a panic purchase of TV - Taxdiscs!

Anyway that's my 99p's worth, and before you ask, No I dont have a tv license, I pay enough taxes as is.

Jump up and down

This chap works for a Tempest manufacturer - we'd better keep his name out of here - and he writes...

TEMPEST has no meaning. But people like to speculate. You can simulate this yourself, by placing an AM radio next to you computer; then, tune the radio up and down the dial until you hear your computer on it. That's what they intercept and reconstruct.

On the other hand

"TEMPEST stands for "Telecommunications Electronics Material Protected From Emanating Spurious Transmissions". Catchy, no?"

No, it doesn't stand for anything. It is a codeword whose meaning is defined as the unwanted dissemination of information by electromagnetic means.

TEMPEST was defined initially by CESG which is a
branch of GCHQ. It's original meaning was classified but is now public domain.

TEMPEST assessments are carried out on equipment, rooms, buildings etc. both in Government and in private sector.

TEMPEST is *not* some sort of great mystery or magical technique. It is a widely studied area which is now much more controlled by regulations such as Radio frequency Interference laws common to the European Community etc.

The TVLA (technical dept.) are not interested in TEMPEST technology as it is exactly the opposite of what they are trying to achieve. They CAN tell what channel and programme you are watching using "their low tech equipment".

I'm sure I used that last piece of tin foil on the turkey...

You might be interested to note that it is possible to intercept VDU emmanations at 1km for monochrome (Black & White) and more for RGB. Both figures are likely to be greater using sophisticated technical
means.

If you are worried that I am reading your VDU, you might consider 'papering' your walls, floor, ceiling, doors and windows with aluminium baking foil. This will greatly reduce the risk but not enough to be
secure. Remember also, power cables and phone lines etc. leaving your 'baking' room.

Regards. Gatekeeper

"What, us?"

EM emissions from electronic devices have long been a source of worry for organisations carrying or transmitting sensitive information. I imagine that
even the IBM golfball typewriter's keystrokes could be monitored by "listening" devices. Typically, most counter-measures have concentrated in the government/military arena, where the research bases at GCHQ Cheltenham and RSRE Malvern and in the USA, the National Security Agency, have long developed and maintained NATO MilSpec standards for manufacturers to comply with.

When working for several major IT vendors in the 1980s, during a demonstration of intercept techniques, I was informed that it was possible to pick up a screen/PC signature as much as a mile away from source! Various well known systems houses were contracted by Govt to provide quality assurance services and compliance certificates for manufacturers' wishing to sell computer equipments to the (secret) state. This is all public domain
stuff, if you read the relevant magazines. It's conceivable that such counter-measures are now included in manufacturers' production runs as
standard nowadays; otherwise, I imagine electronic intercept of, say, Bank of England information is perfectly possible if they don't use other means
of protecting their electronic environments (safe cages for operators for example).

As for television intercept by the TVLA, the TVLA must be being disingenuous when it says it doesn't know about TEMPEST tested equipment precisely because it's using low-level intercept equipment (to detect unpaid TV licensees using their sets) that TEMPEST is supposed to defeat! ®

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