Sunday, December 21, 2008

wikileaks in a jam

Vexation about the publication on Wikileaks of some US Army documents with details of the counter-IED radio jammers. Well, you can see why they're concerned; but I very much doubt this is particularly important.

Recap: the New-Old Iraqi Army was in the habit of using command-detonated IEDs to blow up Coalition and Iraqi government road convoys. To begin with, the command element was often either a GSM device or else some sort of el cheapo radio device like a garage-door opener, RF thermostat, bits and pieces from an industrial process-control rig or the like. After much spending and much fuss, the US Department of Defense deployed "secret" but much hyped jammers on the lead vehicles in the convoys.

Now, there was almost certainly no reason to spend anywhere as much as they did. This is directly linked to the non-fuss about Wikileaks. The devices we have just mentioned have an internationally-standardised frequency band to chatter away in - the so-called Industrial Scientific Medical band, which is unlicensed spectrum - anyone can use it for anything, so long as they don't use too much power. Among other things, all the world's WLAN access points work in the ISM 2.4GHz band, as do wireless hi-fi speakers, baby monitors, cheap CCTV cams, etc, etc. So right back in 2003, it was blindingly obvious which frequencies were involved and what an upper bound on the power output would be. Which made the problem of jamming it pretty simple - just hammer away in the ISM with noise at a significantly higher Tx wattage.

Radio waves are electromagnetic radiation, and therefore their intensity changes with the inverse square of the distance from the source. So you could trivially calculate how much power you need to trigger the device a given distance away from the target. All you need is something that will radiate in the ISM band on command, like...a WLAN card, which now costs about five quid (or, perhaps, a door opener with a better antenna...). I have to say, I suspect that Donald Rumsfeld got played terribly over this. And, of course, nothing radio-frequency stays secret once you start transmitting; everyone can hear you.

There are cleverer things you can do; regarding the GSM ones, you could carry a malicious base station around with you, and therefore blackhole all traffic to and from phones in range. Or you could tap the phones and find out whodunnit (we know the other side do it to us). If I was really serious about this, I'd use one of these, which can be programmed to emulate pretty much anything radio.

So, like so much government secrecy, this is much more to do with security from embarrassment (we spent $billions on technology that would have been cutting edge in 1940!) than security from anything else.

1 comment:

The Great Simpleton said...

Your analyses is correct if we assume the enemy is using the simple devices you describe.

It is quite easy to envisage more sophosticated systems that have more protection and can resist the "throwing shit" philosophy of a simple jammer before they are triggered. If the enemy knew the power of the jammers they could build a receiver that was protected against the jammer (just reduce sensitivity). Their own transmitter then needs to be able to deliver a greater power than the jammer.

This isn't that difficult as the jammer needs to be omni directional and therefore use lower gain antennas. The insurgents, knowing where the bomb is, can use highly directional antennas ith high gain to help generate that extra power. The downside is that whoever triggers the bomb needs to have line of sight to it and so is vulnerable to the blast if too close or being seen before triggering the bomb.

I know that this is all theory but given the length of the war not beyond the wit of AQ to organise.

You should also remember that with electronic warefare it is not what you do its how you do it and how succesful you are that counts. With this in mind it was probably not very helpful to have the technology published, although I agree with the commenter that it was likely to be known to AQ by that point anyway.

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