Steve Evans, BBC News, Seoul
The denial by North Korea is unlikely to convince everyone. Defectors from the North said there was a unit of the military there called Bureau 121 which hacks the websites of foreign organisations.
In March last year hackers calling themselves the Dark Seoul Gang attacked the systems of South Korean banks and television stations. Experts say the methods were similar to the attack on Sony Pictures.
North Korea is an isolated country developing nuclear weapons and ruled by a despot so the increased irritation in Pyongyang on top of Sony's apparently new intention to release the controversial film, perhaps on the web, is causing heightened anxiety in the region.