US slaps on the wardriver-busting paint

Bill Stewart bill.stewart at
Sun Jan 16 12:38:39 PST 2005

At 10:00 AM 1/16/2005, Major Variola (ret) wrote:

>At 09:35 AM 1/14/05 -0500, R.A. Hettinga wrote:
> >It only remains for us to say that DefendAir costs a cool
>$69 per gallon (US gallon, presumably).
>How much is the TV tax in the UK?  How long to pay off the costs of
>paint to hide one's IF oscillator from the White Vans?

You weren't reading the "how it works" description carefully.
It works by blocking RF, so if you put enough paint on to block
outgoing RF from your IF oscillator, you'll also block
incoming RF headed for your tuner, unless your TV set
does a good job of isolating the IF from the antenna.

Similarly, if it's doing a good enough job of blocking RF
to keep 802.11 WLANs from getting out, it's also keeping
cell phone signals from getting in.

RF is surprisingly leaky stuff.  Back when I ran a
TEMPEST-shielded room, we'd find easily-measurable leaks
if the copper-wool filler in the joints wasn't packed tightly,
or if we stuck a paper clip in one of the fiber-waveguide holes.
We were measuring at 450 MHz, which was a really high frequency
for the mid 1980s when computers ran at 10 MHz,
and our room was about 120 dB tight when everything was working.

Looks like the tax is UKP 116, so if the paint is only sold
in whole gallons, and the white vans come around monthly to test,
it could pay off in 3-4 months if it worked, except that
it probably won't work.

Bill Stewart  bill.stewart at 

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