>> bureau 121, a shadow agency with an unknown number of the regime's hand-picked shadow agents placed in countries around the world. chung believes there are approximately 1800 of them. though he said the agents themselves don't know how many exist. we can't verify jong's claims about the shadow group, but he said he's obtained from a current operative hundreds of financial files hacked from south korean banks, complete with names and other bank account details. >> is this the cyber war the real war for north korea? >> translator: raising cyber agents is fairly cheap. the world has the wrong view of the north korean state, with that incorrect world view, north korea was able to increase the ability to launch cyber attacks. >> reporter: south korea learned the hard way. banks across the country last year were paralyzed. atms frozen for days. media outlets went dark and services jammed or white. north korea denied it was the