The US DOJ has disrupted the implementation of the "Cryptolocker" and "Gameover Zeus" trojans, by seizing servers and redirecting traffic away from them to fake servers, according to some news stories, including this one from ABC, here. (See earlier story on Nov. 15, 2013).
Cryptolocker would demand ransom (in bitcoin) to return files to an infected user that had been wiped out (and that would propagate onto any cloud saves, which is one reason it's still a good idea to make offline baclups anyway).
The DOJ is trying to apprehend Russian hacker Evgenly Bogachev, although success in doing so seems unlikely given strained US-Russian relations, over issues like the Ukraine, Edward Snowden, and even the anti-gay law. In fact, Russia's business model these days seems to be predicated on criminal enterprises to steal money from US companies and even individuals.