North Korea offers US joint investigation of Sony cyberattack

North Korea proposed a joint investigation with the US into the hack attack against Sony Pictures, according to the state news agency, KCNA.
The offer comes as the FBI formally accused Pyongyang of the attack on Friday, and US President Barack Obama promised to “respond proportionally” to the online breach, RT reported.
North Korea says it can prove it has nothing to do with the cyberattack on Sony, the KCNA news release said.
The statement by Pyongyang also warns of "grave consequences" if Washington refuses to cooperate in the investigation of the attack, and continues to accuse North Korea.
Sony’s network was hacked in November, with masses of private data, including employees’ emails, being made public.
The attack was followed by threats against movie theaters that planned to show “The Interview,” a comedy in which the US intelligence seeks to kill North Korea's leader Kim Jong-un. Sony eventually refused to release the film.