Required reading for Threepers. How a crowbar and a bunch of amateur burglars brought down COINTELPRO: “The intent of Cointelpro was to destroy lives and ruin reputations.”

Burglars Who Took On F.B.I. Abandon Shadows

Other news organizations that had received the documents, including The New York Times, followed with their own reports.

Ms. Medsger’s article cited what was perhaps the most damning document from the cache, a 1970 memorandum that offered a glimpse into Hoover’s obsession with snuffing out dissent. The document urged agents to step up their interviews of antiwar activists and members of dissident student groups.

“It will enhance the paranoia endemic in these circles and will further serve to get the point across there is an F.B.I. agent behind every mailbox,” the message from F.B.I. headquarters said. Another document, signed by Hoover himself, revealed widespread F.B.I. surveillance of black student groups on college campuses.

But the document that would have the biggest impact on reining in the F.B.I.’s domestic spying activities was an internal routing slip, dated 1968, bearing a mysterious word: Cointelpro.

Neither the Media burglars nor the reporters who received the documents understood the meaning of the term, and it was not until several years later, when the NBC News reporter Carl Stern obtained more files from the F.B.I. under the Freedom of Information Act, that the contours of Cointelpro — shorthand for Counterintelligence Program — were revealed.

Since 1956, the F.B.I. had carried out an expansive campaign to spy on civil rights leaders, political organizers and suspected Communists, and had tried to sow distrust among protest groups. Among the grim litany of revelations was a blackmail letter F.B.I. agents had sent anonymously to the Rev. Dr. Martin Luther King Jr., threatening to expose his extramarital affairs if he did not commit suicide.

“It wasn’t just spying on Americans,” said Loch K. Johnson, a professor of public and international affairs at the University of Georgia who was an aide to Senator Frank Church, Democrat of Idaho. “The intent of Cointelpro was to destroy lives and ruin reputations.”