Stronger encryption in Apple's iPhones and on websites like Facebook has "petrified" the U.S. government because it has made it harder to spy on communications, Glenn Greenwald, the writer who first reported on Edward Snowden's stolen files, told CNBC.

Former National Security Agency (NSA) contractor Edward Snowden caused major shockwaves around the world in 2013 when he unveiled the surveillance body's wide ranging spying practices, which included regularly attempting to snoop of data held by major technology companies.

Glenn Greenwald, the man who helped Snowden publish the documents, said that Silicon Valley companies have bolstered the encryption on their products, thereby making it harder for governments to eavesdrop.

"They (Apple) are now starting to put serious encryption technologies in their new iPhones in their new releases and this has really petrified governments around the world," Greenwald told CNBC in an interview at tech fair CeBIT in Germany.

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