iran may indeed have helped. because they have worked together on missile development for many years, because iran has been a major client of north korea weapons. >> reporter: cnn reached out to iranian officials about that. they didn't respond. the white house maintains north korea acted alone. >> we've got no indication north korea was acting in conjunction with another country. >> reporter: north korea denies hacking sony but if pyongyang pulled this off without any outside help, it would be the greatest success for their shadowy hacking group called bureau 121. >> frankly, north korea, probably doesn't immediate the help. they've been investing in their own siper capabilities for the last four or five years very heavily. they've had a couple of trial runs with attacks on south korean media and banks. >> reporter: one analyst points to a key reason why other governments may not have helped north korea with the sony hack. he says most governments wouldn't be foolish enough to hand any kind of attack tools to north korea, given their erratic behavior. brian todd, cnn, washington.