The United States has determined that North Korea is responsible for the cyber-attack on Sony Pictures Entertainment that scared the moviemaker into cancelling the planned release of a comedy film, the FBI announced Friday.

"As a result of our investigation, and in close collaboration with other U.S. Government departments and agencies, the FBI now has enough information to conclude that the North Korean government is responsible for these actions," the FBI said in a statement Friday.

The attack on Sony reaffirmed that cyber-threats "pose one of the gravest national security dangers to the U.S.," the FBI said, adding that the "destructive nature of this attack, coupled with its coercive nature, sets it apart" from other cyber-intrusions.

"North Korea's actions were intended to inflict significant harm on a U.S. business and suppress the right of American citizens to express themselves. Such acts of intimidation fall outside the bounds of acceptable state behavior," it said.

North Korea had been suspected of involvement in last month's cyber-attack on Sony from the beginning because the communist nation has expressed strong anger at the controversial movie about a plot to assassinate North Korean leader Kim Jong-un.

The film, "The Interview," tells the story of two American journalists who land an interview with the North Korean leader in Pyongyang but are then recruited by the CIA to kill him. Pyongyang has condemned the movie as the "most undisguised" sponsoring of terrorism.

On Wednesday, Sony ultimately decided to call off the film's release, which had been set for Christmas Day, after hackers threatened attacks on theaters showing the movie, and some large theater chains decided to pull the film from their screens.

North Korea has denied involvement, though it lauded the cyber-attack as a "righteous deed."

The FBI said that the data deletion malware used in this attack revealed links to other malware that the FBI knows North Korean actors previously developed. There were similarities in specific lines of code, encryption algorithms, data deletion methods, and compromised networks, it said.

The agency also said that it observed a significant overlap between the infrastructure used in the attack and other malicious cyber-activity that has previously been linked directly to North Korea. It also said the tools used in the attack have similarities to a cyber-attack in March of last year against South Korean banks and media outlets. (Yonhap)