Russia has disputed this (no...really?). I think it's hilarious. I would love to hear anyone in our government try to criticize Putin for this lol. All Putin has to say is (imagine it in a Russian accent) "What? Its just a little thumbdrive! Nothing like what you Americans have done." This is a classic, 80's KGB style move right here.
Russia 'spied on G20 leaders with USB sticks' - Telegraph