From pen registers and PGP to facebook, a look at government snooping through the years

From a 1970s criminal case setting precedent on phone record collection to the Navy roots of the Tor Project and the National Security Agency's 2005 wiretapping debacle, the history of United States government surveillance over the last few decades has had a strong Maryland flavor. In recognition of this week's data-collection scandal, here's a far-from complete list highlighting some notable events:

Secret program mines Web data

By Barton Gellman and Laura Poitras, The Washington Post

WASHINGTON — The National Security Agency and the FBI are tapping directly into the central servers of nine leading U.S. Internet companies, extracting audio, video, photographs, emails, documents and connection logs that enable analysts to track a person's movements and contacts over time.

The highly classified program, code-named PRISM, has not been disclosed publicly before. Its establishment in 2007 and six years of exponential growth took place beneath the surface of a roiling debate over the boundaries of surveillance and privacy. Even late last year, when critics of the foreign intelligence statute argued for changes, the only members of Congress who know about PRISM were bound by oaths of office to hold their tongues.

An internal presentation on the Silicon Valley operation, intended for senior analysts in the NSA's Signals Intelligence Directorate, described the new tool as the most prolific contributor to the President's Daily Brief, which cited PRISM data in 1,477 articles last year. According to the briefing slides, obtained by The Washington Post, "NSA reporting increasingly relies on PRISM" as its leading source of raw material, accounting for nearly 1 in 7 intelligence reports.

It is all the more striking because the NSA, whose lawful mission is foreign intelligence, is reaching deep inside the machinery of American companies that host hundreds of millions of American-held accounts on American soil.

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Image credits: Baltimore Sun file, handout via Reuters, Baltimore Sun file, Getty Images, Getty Images