Report Points to Russian Double Agent, by Clifford J. Levy. The New York Times, November 11, 2010.
MOSCOW — A Russian newspaper reported Thursday that a senior official in Russia’s Foreign Intelligence Service had provided the information that enabled the United States to break up a ring of Russian sleeper spies in June.

The turncoat official, identified only as Colonel Shcherbakov, was said to have defected to the United States just before the arrests and was now being tracked by a Russian assassination squad, according to the newspaper, Kommersant, considered one of Russia’s most authoritative.