FBI: North Korea responsible for Sony hack

North Korea is officially responsible for the cyberattack on Sony Pictures, the FBI announced Friday.

An FBI investigation linked the malware, infrastructure and techniques a group of hackers called “Guardians of Peace” used in the Sony attack to previous North Korean cyberattacks. The North Korean-backed hackers broke into Sony’s servers, published private emails and information and threatened to attack movie theaters screening “The Interview,” a comedy film about an assassination plot on North Korean leader Kim Jong Un.

The FBI called North Korea’s actions “outside the bounds of acceptable state behavior” in a statement released Friday and called cyberthreats “one of the gravest national security dangers.”

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

The investigation linked the “tools” of the Sony hack to North Korean cyberattacks in March 2013 against South Korean banks and media outlets.

U.S. officials have said the government will retaliate for the attacks and White House Press Secretary Josh Earnest said the response would be “proportional.”

“Working together, the FBI will identify, pursue, and impose costs and consequences on individuals, groups, or nation states who use cyber means to threaten the United States or U.S. interests,” the FBI said in the release.