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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 journalist 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 on data held by major technology companies.

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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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Apple, Google, Facebook and Yahoo are some of the major companies that have been in the spotlight after Snowden's revelations. Information from Snowden documents released earlier this month detailed how the CIA had been trying for a decade to crack the security in Apple's products. And last year, Yahoo revealed that it was threatened with a $250,000-per-day fine if it didn't hand over data to the NSA.

The tech giants have been taking major steps to make sure their communications are safe from spying, a move Greenwald –- who won a Pulitzer prize for his reporting on the topic -– said was motivated by the fear of losing customers rather than care for data privacy.

"I don't…(think) they suddenly care about privacy," Greenwald said.

"If…you're a Facebook executive or an Apple executive, you're extremely worried that the next generation of users…are going to be vulnerable to the pitch from Brazilian, and Korean and German social media companies where they advertise and say don't use Facebook and Google because they'll give your data to the NSA."