Blamed ... the Obama administration has formally accused the North Korean government for the Sony hack. Picture: AP Source: AP

Threats issued after the November attack prompted the movie giant to cancel the Christmas Day release of The Interview, in a move that was criticised by US President Barack Obama.

Speaking at a press conference on Friday, Mr Obama said Sony “make a mistake” in pulling the satirical film about North Korea after threats made by hackers.

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Canned ... James Franco and Seth Rogen in a scene from the The Interview. Picture: AP Photo/Columbia Pictures, Sony Source: AP

“I’m sympathetic to the concerns that they faced. Having said all that, yes, I think they made a mistake,” Mr Obama said.

“We cannot have a society in which some dictator some place can start imposing censorship here in the United States.”

His comments came as the hacker group, known as Guardians of Peace, reportedly praised Sony’s “very wise decision” to pull the film and demanded that it never see the light of day.

“Now we want you never let the movie released, distributed or leaked in any form of, for instance, DVD or piracy,” the hackers said in an email obtained by CNN. “And we want everything related to the movie, including its trailers, as well as its full version down from any website hosting them immediately.”

Shelved ... workers remove a poster for ‘The Interview’ from a billboard in Hollywood after Sony cancelled the movie’s release. Picture: AFP Source: AFP

The email warns studio executives that “we still have your private and sensitive data” and claims that they will “ensure the security of your data unless you make additional trouble.”

Sony has already seen the release of a trove of embarrassing emails, scripts and other internal communications, including information about salaries and employee health records.

The FBI said on Friday that it now has enough information to conclude that the North Korean government was responsible for the cyber attack.

“Such acts of intimidation fall outside the bounds of acceptable state behaviour,” the agency said in a statement.

Weighing in ... President Barack Obama says it was a mistake to pull “The Interview”. Picture: AP Source: AP

The attackers used malware to break into the studio and render thousands of Sony Pictures computers “inoperable,” forcing the company to take its entire network offline, the FBI said.

It said analysis of the software tools used revealed links to other malware known to have been developed by “North Korean actors.” It also cited “significant overlap” between the Sony attacks and other “malicious cyber-activity” with direct links to Pyongyang, and said it bears the hallmarks of an attack on South Korean banks carried out by North Korea.

“We are deeply concerned about the destructive nature of this attack on a private sector entity and the ordinary citizens who worked there,” the FBI said.

It wasn’t us ... North Korea has denied involvement in the Sony hack. Picture: AFP Source: AFP

Pyongyang has so far denied involvement in the brazen November 24 cyber attack, but nevertheless hailed it as a “righteous deed.” The North’s top military body, the National Defense Commission, slammed Sony for “abetting a terrorist act while hurting the dignity of the supreme leadership,” according to state news agency KCNA.

The FBI nevertheless warned the attack would not go unpunished. The agency said it would “identify, pursue, and impose costs and consequences on individuals, groups, or nation states who use cyber means to threaten the United States or US interests.”

Senior Republican lawmaker John McCain — the incoming chairman of the Senate Armed Services Committee — went further, calling the cyber attack an “act of war.” But the FBI statement appeared to indicate the US government was treating the incident as more of a criminal act.