banks. >> reporter: federal prosecutors wouldn't comment when contacted by cnn, but tonight, "the wall street journal" reports prosecutors are investigating north korea's possible role in the heist. officials at the cybersecurity firm symantec, which researched this case, tell cnn, the malware code used in this bank hack is similar to the code used in the sony pictures hack back in 2014, which the fbi blamed on north korea. and a top nsa official says the agency is aware of the reported sony similarities. >> if that attribution is true, if that linkage from sony actors to the bangladeshi bank actors is accurate, that means a nation state is robbing banks. >> reporter: kim has an army of hackers, said to number as many as 6,000, working for north korea's notorious reconnaissance bureau, including an elite unit called bureau 121. sources say this kind of cyber heist would be an understandable