Philby's breach of the secrecy surrounding Bentley's defection foiled a year-long attempt by the FBI to employ her as a double agent. Additionally, because of the shutdown of Soviet espionage activity, FBI surveillance of the agents Bentley had named turned up no evidence which could be used to prosecute them. About 250 FBI agents were assigned to the Bentley case, following up leads she had provided and (with phone taps, surveillance and mail interception) investigating people she had named. The FBI, grand juries, and congressional committees would eventually interview many of these alleged spies, who invoked their Fifth Amendment right not to testify or maintained their innocence. For Hoover and a few highly-placed FBI and army intelligence personnel, the corroboration of Bentley's was the late-1940s-to-early-1950s Venona project decryption of wartime cables between Soviet intelligence agents and Moscow. Bentley was referred to in the cables by the codename she had given the FBI, and several of her known contacts and documents she was known to have passed to the Soviets were discussed. The classified Venona project was considered so secret that the U.S. government was unwilling to expose it by allowing its material to be used as evidence in a trial. Neither Presidents Franklin D. Roosevelt or Harry Truman were aware of the project by name, although the presidents received some of its conclusions as summaries by J. Edgar Hoover in weekly intelligence reports. Public testimony With chances of successful prosecution looking unlikely, Hoover gave the names of some of Bentley's contacts to members of Congress with the understanding that the accused spies would be questioned by Congressional committees. He believed that the public suspicion and accusations would be enough to ruin their careers. Attorney General Tom C. Clark presented the Bentley case to a grand jury, although he had little hope of any indictments. Bentley testified before this grand jury several times before April 1948, and details of her case began to leak to the press. Bentley decided to reveal her full story herself to retain more control, and met with New York World-Telegram journalists Nelson Frank and Norton Mockridge. On four consecutive days, the newspaper published a series of front-page stories about the unnamed "beautiful young blonde" who had exposed a ring of spies: "Red Ring Bared by Blond Queen" (July 21, 1948); "Super-Secrecy Veiled Russia's Spy Cells Here" (July 22, 1948); "Citizens Tricked into Spy Ring by U.S.