President Lyndon B. Johnson meeting with members of his civil rights cabinet on 18 January including, from left to right, Martin Luther King Jr., Whitney Young, and James Farmer. King and Young were both future targets of the NSA watch list system. (Photo from Lyndon B. Johnson Presidential Library, On-line Photo Archive, W425-21).

As Vietnam War protests grew, the U.S. National Security Agency (NSA) tapped the overseas communications of prominent American critics of the war — including a pair of sitting U.S. senators. That's according to a recently declassified NSA history, which called the effort "disreputable if not outright illegal."

The identities of the NSA's surveillance targets were kept secret for decades, but an Interagency Security Classification Appeals Panel decision in response to an appeal by the National Security Archive at George Washington University, has resulted in the declassification of these NSA records for the first time.

Read more at the National Security Archives (not to be confused with the National Security Administration, also known as the NSA).