The Secret NSA Surveillance program PRISM EXPOSED

Ex-CIA employee, Edward Snowden, working as a contractor at the U.S. National Security Agency says he leaked details of a top secret U.S. surveillance program, Prism, acting out of conscience to protect "basic liberties for people around the world."

The National Security Agency has obtained direct access to the systems of Google, Facebook, Apple and other US internet giants, according to a top secret document obtained by the Guardian.

The NSA access is part of a previously undisclosed program called PRISM, which allows officials to collect material including search history, the content of emails, file transfers and live chats, the document says.

The Guardian has verified the authenticity of the document, a 41-slide PowerPoint presentation -- classified as top secret with no distribution to foreign allies -- which was apparently used to train intelligence operatives on the capabilities of the program. The document claims "collection directly from the servers" of major US service providers.