Why tapping mobile calls is 'trivial'

Angela Merkel using mobile
Image caption Ms Merkel is known for her heavy use of her mobile phone

The allegations that American spies have been tapping the phone of the German Chancellor Angela Merkel have sparked a political storm. But just how easy is it to listen to mobile phone calls?

In theory, it has become a lot harder since the advent of the 3G networks, where calls are encrypted with technology which so far appears not to have been cracked. But Steve Gold, a former hacker who is now the editor of IT Security Pro, does not believe that would have been insuperable for the Americans.

"For very little, you can buy something that will jam all calls over 3G and 4G, and force them back onto the GSM network," he explained. The GSM security system dates back to the late 1980s, and cracking that, he says, would be "relatively trivial."

Intelligence agents could set up an "evil twin" or rogue base-station which, in conjunction with the jammer, would mean that all mobile calls made in the vicinity could be intercepted. "You could put the equipment necessary into a suitcase and do the whole thing for under £1000," said Mr Gold."It isn't rocket science."

A telecoms security consultant, who preferred not to be named, speculated that intelligence agencies would be more likely to seek access to calls via the mobile operators. In the United States the National Security Agency obtained a court order allowing it access to the mobile phone records of Verizon customers, but overseas the challenge would be greater. "But it is not unknown for intelligence agencies to use tame insiders at telephone companies to get access to calls," said the consultant. In 2010, an employee of the Lebanese state telecom firm was arrested on suspicion of spying for Israel.

The German government was in the process of beefing up the security of its mobile phones.

Carsten Michel of Secusafe told the World at One that his firm was supplying a system which involved installing hardware on every phone to encrypt voice calls.

But it seems this protection was not in place for Angela Merkel when the alleged interception took place: "We are rolling this out as we speak, so presumably she wasn't using this solution," said Mr Michel. "The German Federal government has been thinking about this for years."

The diplomat and former chairman of the Joint Intelligence Committee Sir Rodric Braithwaite said he was not surprised by the revelations. "Everybody was spying on everybody during the Cold War and it didn't just stop after the fall of the Soviet Union," he told the World at One.

Sir Rodric had this advice on security for politicians: "It's a pretty good rule of thumb that if you don't want people to listen to what you're saying you shouldn't use a telephone or send an email."