Every company involved denied the most sensational assertion in the Prism documents: that the NSA pulled data "directly from the servers" of Microsoft, Yahoo, Google, Facebook, AOL and more.
Technology experts and a former government official say that phrasing, taken from a PowerPoint slide describing the program, was likely meant to differentiate Prism's neatly organized, company-provided data from the unstructured information snatched out of the Internet's major pipelines.
In slide made public by the newspapers, NSA analysts were encouraged to use data coming from both Prism and from the fiber-optic cables.
Prism, as its name suggests, helps narrow and focus the stream. If eavesdroppers spot a suspicious email among the torrent of data pouring into the United States, analysts can use information from Internet companies to pinpoint the user.
With Prism, the government gets a user's entire email inbox. Every email, including contacts with American citizens, becomes government property.
Once the NSA has an inbox, it can search its huge archives for information about everyone with whom the target communicated. All those people can be investigated, too.