25 Oct 2013

So how did the NSA eavesdrop on Angela Merkel’s mobile calls?

Another day, another revelation from the cache of documents taken by the whistleblower Edward Snowden.

This time, the National Security Agency has apparently appealed to other US government departments for the mobile numbers of world leaders, which it then claims to be able to monitor.

From the few lines of text, it’s hard to divine much detail – but that hasn’t diminished the outrage felt by the German and French leaders, who claim they’ve felt the sharp end of the surveillance.

How was it done? When you make a mobile phone call, the signal is sent to a nearby cell tower, transferred along cables to a larger interchange, and at some stage hits the country’s communications backbone. Most countries have a tier 1 provider that handles traffic at a national level – in the UK, that’s BT.


International traffic is sent between Tier 1 providers mainly via undersea cables from landing points such as Bude in Cornwall.

If the NSA wants to monitor calls they have several ways of doing so. At a basic level, if they get close enough to the phone they can capture the 3G signal it gives out using hardware that’s widely available over the internet. Another option is to secretly recruit someone in the country’s tier 1 provider to install surveillance software. (These might fall under the category of “traditional spycraft”).

Another option is to go straight to the country’s mobile network providers and request surveillance on a particular number. The NSA can’t compel every country’s comms firms to comply, but it can point out that the consequences of falling out of favour with the USA are not good.

Lastly there are the international agreements, under documents such as the UKUSA agreement, which commits the British and American governments to information sharing.

It’s naive to think there are neat, official ways of doing all this. Intelligence staff work secretly, they develop relationships with kindred spirits in foreign countries’ agencies, and are given autonomy to work those relationships to fulfil their goals.

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