Dmitry Medvedev has confirmed that he knew about the double-agent within Russia’s foreign intelligence service who told the FBI about the Russian spy ring operating in the U.S. The admission, which is embarrassing for Russia’s SVR foreign intelligence service, came as experts said that more Russian spies were likely to still be operating in the United States undetected. At the G20 summit in South Korea, Medvedev said he knew Colonel Scherbakov had betrayed the ten Russian spies. The ten spies were exchanged in July for four men Russia was holding as Western agents in the biggest spy swap since the Cold War. Medvedev said Russia needs to learn lessons from the fiasco and that an investigation was under way. However, he said he would no sack the head of Russia’s foreign intelligence service, Mikhail Fradkov, who has been the subject of dismissal talk.