30-year-old American Edward Snowden, a contract employee at the National Security Agency, is the whistleblower behind significant revelations that surfaced in June 2013 about the US government's top secret, extensive domestic surveillance programmes. Snowden flew to Hong Kong from Hawaii in May 2013, and supplied confidential US government documents to media outlets including the Guardian.
Apple denies 'backdoor' NSA access to iPhones
Germany's Der Spiegel reveals secretive unit of the NSA developed specialist software to spy on iPhones
Apple has denied any knowledge of a National Security Agency tool to hack into iPhones after newly released documents showed the company's smartphone was targeted by the US spy agency.
Documents released on Monday showed the NSA had worked on software that would allow it to remotely retrieve virtually all the information on an iPhone including text messages, photos, contacts, location, voice mail and live calls.
The software, DropoutJeep, was first disclosed by Der Spiegel and security researcher Jacob Appelbaum. The NSA slides are dated 2008.
In a statement, Apple said: "Apple has never worked with the NSA to create a back door in any of our products, including iPhone. Additionally, we have been unaware of this alleged NSA program targeting our products. We care deeply about our customers' privacy and security. Our team is continuously working to make our products even more secure, and we make it easy for customers to keep their software up to date with the latest advancements.
"Whenever we hear about attempts to undermine Apple's industry-leading security, we thoroughly investigate and take appropriate steps to protect our customers. We will continue to use our resources to stay ahead of malicious hackers and defend our customers from security attacks, regardless of who's behind them."
According to the slides, DropoutJeep required "close access methods" in order to be installed on an iPhone, meaning NSA agents would need physical access to the device. One slide says a "remote installation capability will be pursued for future use".
The NSA said it did not comment on any specific allegations but added that its interest "in any given technology is driven by the use of that technology by foreign intelligence targets".
Additional reporting by Associated Press