In 1995, the National Security Agency publicly released documents from the VENONA project, an effort to decrypt intercepted communications between Soviet agents and the NKVD/KGB. A 1944 cable from New York City to Moscow clearly indicates that a spy with the code named ANTENNA and later LIBERAL (who the Federal Bureau of Investigation later decided was Julius Rosenberg) was engaged in espionage for the Soviet Union, though the importance of the activities of LIBERAL/ANTENNA is not clear, particularly considering that the Soviets were receiving information on the atomic bomb from Klaus Fuchs, Donald Maclean and Theodore Hall. From the VENONA transcripts alone, one could make a strong case that Ethel was never a spy. A document from November 27, 1944 <2> specifically about "LIBERAL's wife" who is identified with the first name, Ethel, lists her as a "fellow countryman" and claims that she was aware of Julius's work. "LIBERAL's wife" Ethel was never assigned a code name—the only reference to her states she "does not work." Meredith Gardner, the Russian linguist who worked intensely on the VENONA decryptions, was quoted as saying that the work statement indicates that "LIBERAL's WIFE," Ethel, was not an espionage agent. Julius was always referred to as "ANTENNA" or "LIBERAL", never by his own name—which has led some to doubt that the FBI's connection of "LIBERAL" to Julius Rosenberg was accurate, but the preponderance of opinion is that LIBERAL/ANTENNA does refer to Julius Rosenberg.
In his memoirs, published posthumously in 1990, Nikita Khrushchev praised the pair for their "very significant help in accelerating the production of our atomic bomb." Alexander Feklisov, a former KGB officer, disagreed, stating that the information given was "meaningless".<8>
Faced with the VENONA transcripts and periodic revelations from former Soviet intelligence officials and archives, most critiques of the Rosenbergs' prosecution today has shifted towards the usefulness of classified nuclear information allegedly provided by Julius Rosenberg and David Greenglass to the Soviet Union, the severity of their punishment, and the fact that not all Soviet spies were caught, and not all who were caught were prosecuted by the U.S. government. The atom bomb information that Greenglass claimed to have given to the Soviets appears to have been quite poor in comparison to the information given by Fuchs, who had a much more intimate understanding of the research being done (revealed by records of Fuchs' detailed transmissions in selective releases from Soviet archives) and a much more sophisticated theoretical understanding of the mechanisms of the bomb. There was also significant information provided independently of Fuchs by the young scientist Theodore Hall, as well as potentially more agents, the identities of whom have not yet been fully established.
http://en.wikipedia.org/wiki/Rosenbergs