If you can get the cellphone companies to cooperate: develop a system that inhibits cellphones ringing in the vicinity of moving convoys. You can use a system that sends GPS coords to a computer, which then sends (encrypted challenge-response) inhibit messages to the towers close by the convoy.
Although this solution and the solutions mentioned in the above threads are technically sound, I am aghast at the sincerity with which they were suggested.
It is not appropriate to interfere with such a crucial piece of infrastructure. In developing countries especially, cell phones are the only link many people have. They run their small businesses, allow people to call family to see if they have been hurt, etc.
Would you tolerate something like this in your Country? Shut down the internet for a little while to prevent a terrorist threat?
In many cities, specialized police units either already have or are in the process of being issued cell phone jamming units.
They are being issued with these sorts of scenarios specifically in mind. If the police think there's a bomb somewhere, set to be triggered via cell phone, damn right I'd want them to block the cell phones in the local area to keep it from going off.
The problem with cell jamming technology isn't when it's being used to stop bombs from going off, the risk is that it'll be used for more trivial purposes.
Note that the posts above are not advocating disabling the cell network, but they are instead advocating autodialing -- something that is regularly tolerated (although despised) in the U.S.
According to the article, the military is already jamming cell signals along caravan routes, but one has to wonder if it's even noticeable to the locals, given that cell phones are inherently unreliable, especially in mountainous regions. Cell phone jammers are in regular use in other countries, purely for the convenience of their owners: http://en.wikipedia.org/wiki/Mobile_phone_jammer
I keep wondering how sophisticated the insurgents are. If they have some savvy equipment and know-how they can easily modify the software to reject calls from anyone but a hardcoded number.
Well, let me give you an idea how sophisticated they could easily be: Where I live (netherlands) we have a whole bunch of cell phone operators and they all cell their phones together with subscriptions based on sim-lock. These sim-locked phones are usually pretty expensive models sold at a great discount, so there is now a cottage industry of sim-locked phone unlockers.
These people are all at about the same level of tech as the satellite code crackers a couple of years ago, and it isn't rare to see top of the line scopes, all kinds of specialized soldering equipment (including vacuum smd soldering stations) and laptops full of software geared towards getting a cell phone to do something it really doesn't want to do.
This involves forced firmware upgrades, replacing chips on the board (usually eeproms or flashed chips with blank ones to be able to trick the firmware into thinking it is on a new, unused phone).
If any one of these guys gave a seminar for a week or so the 'bad guys' would be in the possession of all the knowledge and gear they would need to do just about anything they wanted, short of rewriting the phones OS completely. And they wouldn't need that because in their world simpler is better, and writing software is a complicated business.
