(Pocket-lint) - The US National Security Agency and Federal Bureau of Investigation have long accessed the internal servers of nine major tech companies in an effort to crop sensitive data like video, photos, audio, emails and documents, according to a recently leaked security presentation.

The Washington Post and The Guardian first revealed the 41-slide presentation that details a highly classified and previously private program, codenamed PRISM, which involves harvested data from companies such as Apple, Microsoft, Yahoo, Google, Facebook, AOL, Skype YouTube and PalTalk.

According to the slides, Microsoft first joined PRISM in 2007. Yahoo followed in 2008, with Google, Facebook and PalTalk coming aboard in 2009. PRISM then added YouTube in 2010, Skype and Aol in 2011, and Apple in 2013. Dropbox, according to the reports, is set to join PRISM soon, while Twitter is notably missing from the roster.

The Washington Post claimed that each company - of its own free will - participated in the six-year-old program that has allegedly contributed to the daily briefings given to US President Barack Obama. In addition, one in seven NSA intelligence reports purportedly contain data from PRISM.

The NSA can retrieve any kind of data from these companies through PRISM, but it has allegedly not tried to collect everything. The leaked presentation said PRISM only began as a method for the NSA to overcome legal limitations found within FISA warrants in regards to "tracking suspected foreign terrorists".

President George W. Bush first allowed the NSA to access such high-level data, but President Obama renewed PRISM in 2012. The slides clarified that the US has a "home-field advantage", because the largest internet companies have headquarters in the US.

Update 1:

In a statement to both The Washington Post and The Guardian, Google has denied the government had access to its servers: "Google cares deeply about the security of our users' data. We disclose user data to government in accordance with the law, and we review all such requests carefully. From time to time, people allege that we have created a government 'backdoor' into our systems, but Google does not have a 'backdoor' for the government to access private user data."

Facebook has also denied any involvement to TechCrunch: ”We do not provide any government organization with direct access to Facebook servers," it said on Thursday. "When Facebook is asked for data or information about specific individuals, we carefully scrutinise any such request for compliance with all applicable laws, and provide information only to the extent required by law.”

Apple also provided a statement on Thursday, to CNBC: "We have never heard of PRISM. We do not provide any government agency with direct access to our servers," it said.

Update 2:

CEO Larry Page further posted on Google's official blog on Friday. He reiterated that the company did not join PRISM knowingly, and he had not heard of PRISM until Thursday when reports about its existence emerged.

In a Facebook post on Friday, CEO Mark Zuckerberg joined the denials and said his company never granted government access to its servers: "We have never received a blanket request or court order from any government agency asking for information or metadata in bulk, like the one Verizon reportedly received. And if we did, we would fight it aggressively".

President Obama delivered his first public statements about PRISM on Friday. Answering a reporter's questions after his speech on healthcare, the President said Congress knew about any and all surveillance programs: "These are programs that have been authorized by broad bipartisan majorities repeatedly since 2006," he said, noting, "your duly elected representatives have been consistently informed on exactly what we're doing."

Writing by Elyse Betters.