UPDATE: Apple, Facebook, Microsoft and Google have all denied involvement in the PRISM program.

EARLIER: A top-secret April PowerPoint slideshow details how the National Security Agency partnered with nine tech companies, including Apple, Microsoft and Google, to monitor users' activity, according to the Washington Post and the Guardian.

According to the presentation, the NSA got direct access to these companies' servers in order to directly watch user communications.

The program, called PRISM, is nominally aimed at foreign actors, but the Post reports that purely domestic communications could easily end up in NSA hands, so long as an algorithm estimated at least a 51 percent probability that they were foreign.

Here are the slides showing how the NSA reportedly got its hands on your data:

The slides reflect that nine companies participate in the program, starting with Microsoft in 2007. The following entrants were Yahoo, Google, Facebook, PalTalk, YouTube, Skype, AOL and Apple. YouTube is a Google subsidiary and Skype is a Microsoft subsidiary.

They say that the NSA gets vast amounts of information from the participating companies — email, chats, videos, photos, stored data, voice-over-IP communications, and more. The companies also take "special requests."

Many foreign communications travel through the U.S., giving the NSA the opportunity to intercept them.