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The FBI has confirmed that the North Korean government is responsible for the cyber attack on Sony Pictures Entertainment in late November, NBC News reports.

A group calling itself the Guardians of Peace claimed responsibility for the hack, which resulted in numerous leaked emails and Sony's cancellation of the release of the Seth Rogen and James Franco movie The Interview, about the assassination of North Korean leader Kim Jong-un, amid threats of terrorism.

"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.

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According to technical analysis, the date deletion malware used to attack Sony was developed by North Korea and features similarities in specific lines of code and encryption algorithms. The FBI also revealed that the Sony hack featured significant similarities in the infrastructure compared to other known cyber attacks the U.S. government has previously linked to 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. "Further, North Korea's attack on SPE reaffirms that cyber threats pose one of the gravest national security dangers to the United States. Though the FBI has seen a wide variety and increasing number of cyber intrustions, the destructive nature of this attack, coupled with its coercive nature, sets it apart. Norht 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."

On Thursday, a White House spokesman called the hack a "serious national security matter" and said that the United States would consider a "proportional response" once the responsible party was confirmed.

Sony has not commented on the FBI's findings.