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From: Toni Heinonen (Toni.Heinonenteleware.fi)
Date: Mon Mar 25 2002 - 04:55:20 CST
> > > How susceptible are various wireless networking implementations to
> > > jamming (as a means to a DoS)?
> While several pages of well written technical fantasy may work for
> marketing, it's generally not a good idea to try feed fluff
> to engineering
> There will always be a greater financial incentive to create marketing
> hyperbole than to rebut it.
Oh, but I can assure you, I have no financial motives here. Actually, I was trying to be as clear about the technical transmission technologies as possible, sorry if I underestimated my audience. The original poster however asked on a very general basis, so I answered accordingly. And by no means did I mean to undermine the threats found in today's wireless networks.
But, to the point.
> A jamming device need not be smart or sophisticated.
> Choose an inverter IC with the appropriate timings, loop 3
> inverters in
> series to generate a nice noisy signal on your base
> frequency. Since it's
> a square wave, you'll have lots of useful sidebands and harmonics.
> Tuning impedances can selectively create a lot of noise
> across multiple
> wide bands.
> Since spreading the noise across more bandwidth decreases the
> power, an output transistor may need to be added. Swamp the
> emitter until
> it's clipping the signal and producing more power on more frequencies.
> Add transistor stages as needed, since each costs about $1.
In the US and Europe, Bluetooth uses frequencies 2.400 MHz to 2.483,5 MHz, with 79 different bands to hop on, each 80 MHz wide or sometimes more. Seeing as you would not try to synchronize your jammer with the hop sequence, do you think it would really be capable of jamming that whole band? After all, even a square wave won't produce that much of a disturbance to the neighbouring bands. I mean, of course you could build a jammer like that, but wouldn't it cost too much? I mean, I see your point:
> It will always be cheaper to DoS a wireless network than it
> is to build
Of course, the whole idea is that the protective safeguards for a system do not cost more than the protected assets. Seeing as how a Bluetooth chip is supposed to cost 5$ (of course not yet, but probably so after mass production), would it really be possible to build a jamming device of this magnitude for 10$ (the cost of a two-machine Bluetooth network)?
Additionally, you did not comment on my analysis of WLAN/UMTS transmission a la DSSS. Do you have any ideas there?
TONI HEINONEN, CISSP
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