NSA Prism System

Inner workings of a top-secret spy program

See below for Prism Slides…

The National Security Agency’s PRISM progam, which collects intelligence from Microsoft, Google, Yahoo, Apple and other tech giants, is “targeted” at foreigners. But it also collects the e-mail, voice, text and video chats of an unknown number of Americans — “inadvertently,” “incidentally” or deliberately if an American is conversing with a foreign target overseas. Here are new details on how the program works, from top-secret documents and interviews.

prism flow

NSA collects, identifies, sorts and stores at least 11 different types of electronic communications













Targeting a “selector”

An NSA analyst types one or more search terms, or “selectors.” Selectors may refer to people (by name, e-mail address, phone number or some other digital signature), organizations or subjects such as the sale of specialized parts for uranium enrichment.

Along with the selectors, the analyst must fill out an electronic form that specifies the foreign-intelligence purpose of the search and the basis for the analyst’s “reasonable belief” that the search will not return results for U.S. citizens, permanent residents or anyone else who is located in the United States.

Accessing private companies’ data

The search request, known as a “tasking,” can be sent to multiple sources — for example, to a private company and to an NSA access point that taps into the Internet’s main gateway switches. A tasking for Google, Yahoo, Microsoft, Apple and other providers is routed to equipment installed at each company. This equipment, maintained by the FBI, passes the NSA request to a private company’s system. Depending on the company, a tasking may return e-mails, attachments, address books, calendars, files stored in the cloud, text or audio or video chats and “metadata” that identify the locations, devices used and other information about a target.

Data processed by NSA computers

The same FBI-run equipment sends the search results to the NSA. The results are first sent for processing by the NSA’s automated system code-named PRINTAURA. This system combines the roles of librarian and traffic cop. PRINTAURA sorts and dispatches the data stream through a complex sequence of systems that extract and process voice, text, video and metadata.

What the analyst sees

For example, a completed PRISM search may yield e-mails, login credentials, metadata, stored files and videos. After processing, they are automatically sent to the analyst who made the original tasking. The time elapsed from tasking to response is thought to range from minutes to hours. A senior intelligence official would say only, “Much though we might wish otherwise, the latency is not zero.”

Checks and balances

The program as a whole is authorized once a year in a secret order from the Foreign Intelligence Surveillance Court. There are no individual warrants, even for access to full content.

Before an analyst may conduct live surveillance using PRISM, a second analyst in his subject area must concur. In this “validation” process, the second analyst confirms that the surveillance has a valid foreign-intelligence purpose, that there is a “reasonable belief” that the target is neither American nor on U.S. territory, and that the surveillance complies with NSA regulations and the classified judicial order interpreting Section 702 of the FISA Amendments Act.

For stored content, a similar review takes place in the NSA’s office of Standards and Compliance. There is a second review by the FBI to ensure that the target does not match a U.S. citizen or U.S. resident in FBI files.


Most “metadata,” or records of the people, locations, equip- ment, times, dates and durations of communications, are collected in programs other than PRISM. Some come from what NSA calls Upstream: interception at the biggest junctions of the internet and telephone networks. Others come directly from telephone companies — AT&T, Verizon Business Services and Sprint — who keep detailed calling records.

Information collected on Americans

If a target turns out to be an American or a person located in the United States, the NSA calls the collection “inadvertent” and usually destroys the results. If the target is foreign but the search results include U.S. communications, the NSA calls this “incidental” collection and generally keeps the U.S. content for five years. There are “minimization” rules to limit the use and distribution of the communications of identifiable U.S. citizens or residents. The NSA discloses the identities to other agencies if it believes there is evidence of a crime or that the identities are essential to understanding an intelligence report.

Upstream program

This slide shows PRISM as only one part of the NSA’s system for electronic eavesdropping. The “Upstream” program collects from the fiber-optic cable networks that carry much of the world’s Internet and phone data. The underlying map depicts the undersea cables that connect North America to the rest of the world.


Acquiring data from a new target

This slide describes what happens when an NSA analyst “tasks” the PRISM system for information about a new surveillance target. The request to add a new target is passed automatically to a supervisor who reviews the “selectors,” or search terms. The supervisor must endorse the analyst’s “reasonable belief,” defined as 51 percent confidence, that the specified target is a foreign national who is overseas at the time of collection.


Analyzing information collected from private companies

After communications information is acquired, the data are processed and analyzed by specialized systems that handle voice, text, video and “digital network information” that includes the locations and unique device signatures of targets.


Each target is assigned a case notation

The PRISM case notation format reflects the availability, confirmed by The Post’s reporting, of real-time surveillance as well as stored content.


Searching the PRISM database

On April 5, according to this slide, there were 117,675 active surveillance targets in PRISM’s counterterrorism database. The slide does not show how many other Internet users, and among them how many Americans, have their communications collected “incidentally” during surveillance of those targets.


Introducing the program

A slide briefing analysts at the National Security Agency about the program touts its effectiveness and features the logos of the companies involved.


Monitoring a target’s communication

This diagram shows how the bulk of the world’s electronic communications move through companies based in the United States.


Providers and data

The PRISM program collects a wide range of data from the nine companies, although the details vary by provider.


Participating providers

This slide shows when each company joined the program, with Microsoft being the first, on Sept. 11, 2007, and Apple the most recent, in October 2012.




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