During the Vietnam War, the NSA used data from Shamrock to compile a watch-list (code-named “Minaret”) of Nixon’s political enemies, including Martin Luther King, Jane Fonda, folksinger Joan Baez and Dr. Benjamin Spock, along with 75,000 other Americans.

Operation Shamrock came to light in 1975 during investigations by the U.S. Senate into government intelligence abuses in the Nixon Administration. The committee, chaired by Sen. Frank Church (D-Idaho), learned that three telegraph companies had turned over all their overseas communications traffic, both outbound and inbound, to the National Security Agency (NSA) on a daily basis for 30 years.