North Korea has denied involvement in a cyber attack on Sony Pictures, but hailed it as a "righteous deed", possibly carried out by its supporters in protest at an upcoming film about Kim Jong-Un.
The Interview, a comedy involving a fictional CIA plot to assassinate the leader of the isolated communist state, has infuriated Pyongyang, which has previously declared it an "act of war", and warned of "merciless retaliation".
The attack, by a group calling itself the Guardians Of Peace, crippled key systems at Sony Pictures, led to the disclosure of personal information about 47,000 employees, and saw blockbuster movies, including Second World War drama Fury starring Brad Pitt, being leaked online.
There has been speculation that the attack was Pyongyang's retaliation for the Sony movie.
North Korea's top military body, the National Defence Commission, rejected reports of its involvement as "false rumour", but criticised Sony for "abetting a terrorist act while hurting the dignity of the supreme leadership of the (North)".
It told the state-run news agency: "The hacking into the Sony Pictures might be a righteous deed of the supporters and sympathisers with the (North) in response to its appeal."
Meanwhile, forensics experts hired by Sony to investigate the massive cyber attack at its Hollywood studio said the breach was unprecedented, well-planned and carried out by an "organised group".
However, no indication is given of who was behind the hacking campaign.
The company has faced accusations of poor security in the wake of the attack, underlined by the revelation that the media giant saved thousands of internal passwords in a folder called 'Passwords'.
Kevin Mandia, the top executive at FireEye Inc's Mandiant forensics unit, said in an email to Michael Lynton, chief executive of Sony Pictures Entertainment (SPE): "The scope of this attack differs from any we have responded to in the past, as its purpose was to both destroy property and release confidential information to the public."
He added: "The bottom line is that this was an unparalleled and well planned crime, carried out by an organised group, for which neither SPE nor other companies could have been fully prepared."
FBI spokesman Joshua Campbell said the agency agreed with the analysis the attack went undetected by standard anti-virus software, but declined to discuss the progress of the investigation.
Daniel Clemens, chief executive of cyber security firm PacketNinjas, said that while the attack was unprecedented in impact "there are many things Sony could have done to prepare and defend against this attack".
