rebuttal to president obama by curiously suggesting that the two countries work together in a mutual investigation to find the real culprit. north korea saying if america refuses there will be serious consequences. kyung lah, cnn, seoul. >> that cyberattack on sony was damaging and sophisticated, perhaps too sophisticated for north korea, according to some experts. brian todd has more on who else might be behind the attack. >> reporter: the cyberforensic evidence all points to north korea, according to the fbi, the computer code, algorithms, the ip addresses. that's not necessarily a clear path to pyongyang. >> it's circumstantial evidence that can be faked. >> reporter: scott borg's cyber security group monitors hackers across the globe. there were elements in the sony attack that went beyond their skill level. >> biggest one is that they were