It’s Not Only Walls That Have Ears

He became suspicious when he noticed his mobile was connected to a UK phone network. It was strange because he was standing in Ireland: that was either one very powerful base station or something strange was happening.


That’s how one member of the Irish government’s GSOC organisation realised his phone was being monitored.

Cell phone calls can be intercepted using a “man in the middle” technique in which the spy sets up a fake base station close to the mobile in question. If it gives the strongest signal, the phone will latch onto the fake one, which in turn connects to the genuine one and passes your call on. All the data from your handset can now be collected and analysed.

Of-course, mobile phone transmissions these days are encrypted, so the spy still needs to break the cipher, but once he has collected the data from your call, he can process it later with powerful computers. This is also where he brings a second technique into use. Data from 4G and 3G systems are a lot harder to crack than those made over the older GSM network. The latter uses 1980’s technology, which is much simpler to decode. If you have a 4G phone, you’ll probably have noticed that it’s not always on a 4G network. That’s because coverage is still sparse: as soon as you leave the city, your phone automatically switches to the best network it can find – either 3G or GSM.

So your spy also brings along a jammer. He blocks all 4G and 3G signals; your phone automatically moves onto GSM and your data is now far more weakly encrypted – a synch for our spy to decrypt. He can make it even easier for himself if you have an older phone – the basic GSM security keys were broken some years ago and posted on the internet. So one other thing he will try is to get his fake base station to instruct your mobile to switch to that older GSM encryption – an older phone will meekly change over and give him even easier pickings on your conversation.


The recent story of the Irish GSOC employee’s cell phone being intercepted in this way has a lovely irony to it because GSOC’s role is to monitor the Irish police force. After an investigation, it was found that the organisation that had arranged the intercept was…. yes: the Irish police! At first I couldn’t help but laugh, but I then wondered whether a police organisation, no doubt cash-strapped these days, wouldn’t do better spending its limited resources targeting criminals instead.

Large government agencies like America’s NSA, of-course, also use similar techniques to gather intelligence. They no doubt target terrorists or criminals but they also seem to be burning resources on intercepting calls made by supposedly friendly parties. Angela Merkel, the German chancellor, recently discovered the NSA had been bugging her phone for the last ten years. That came to light, not because of strange mobile behaviour, but from Edward Snowden’s leaks about America’s Prism programme.

There was an uproar, and the Americans were forced to stop. Some time later, though, it transpired they were bugging ten of her close colleagues instead. Bizarre. True spy thriller material.

So how do you call a friend these days if you want to ensure no-one can eavesdrop on your conversation? Certainly don’t switch to Skype! Carrier pigeon, perhaps? What’s your imaginative way to communicate with a friend so that what you say can’t be intercepted by a spy?



Twitter: @ian_coates_



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