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How agencies spy in the digital age

27 January 2014 Last updated at 01:37 GMT

US intelligence leaker Edward Snowden has alleged the National Security Agency engaged in industrial espionage.

In an interview with Germany's ARD TV channel, the former NSA contractor said the agency would spy on big German companies that competed with US firms.

Gordon Corera explains how agencies spy in the digital world.

Map of the Internet visualisation and data provided by Peer1 Hosting

More on surveillance:

How vulnerable is the internet?

Google calls for new NSA reforms

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