How is the NSA’s vault of secrets being unlocked?

BBC NEWS reported that,
How is the NSA’s vault of secrets being unlocked?

October 30, 2013 03:21A summary of US spying allegations brought about by Edward Snowden's leak of classified documents

By Tara McKelvey BBC News Magazine Media organisations have revealed startling details about US espionage in recent weeks. The disclosures can be traced back to three people who don't play by the rules - intelligence leaker Edward Snowden and his chief disseminators, the Guardian newspaper reporter Glenn Greenwald, and independent film-maker Laura Poitras. The National Security Agency (NSA) reportedly collected data on millions of US customers of Verizon, a telecom firm, and on 60 million calls in Spain. It is also said to have obtained data on 70 million digital communications in France - and spied on Chancellor Angela Merkel for years.
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How is the NSA’s vault of secrets being unlocked? http://www.bbc.co.uk/news/magazine-24677237