The Anglo-American cryptographic project that succeeded in decoding more than 2,000 Soviet messages exchanged between Moscow and various diplomatic posts overseas between 1940 and 1949 had several code names but is generally known as VENONA.
Altogether 750,000 telegrams were examined, including a batch from Sweden supplied in 1966, and an error in the construction of the Soviet one-time pads enabled fragments of the texts to be reconstructed. The traffic ranged from routine consular, trade, and diplomatic messages, to highly sensitive NKVD, GRU, and Naval GRU texts. The analytical work, which identified more than 300 spies, including Alger Hiss, Klaus Fuchs, Donald Maclean, Harry Dexter White, and the Rosenbergs, continued until 1979 but was not declassified until 1995. Although the translated, partially decrypted messages were not admissible in any criminal trial, they provided mole hunters with sufficient information to trace dozens of spies recruited and run by the NKVD and GRU during and after World War II. Although the traffic ceased in 1949, when William Weisband and Kim Philby both warned Moscow of the progress being made by the American and British cryptanalysts, prompting a change in Soviet cipher procedures, there was sufficient material for MI5 and the Federal Bureau of Investigation to study in an effort to put real names to the often transparent code names used to protect the true identities of spies.