The U.S. government believes that North Korea is behind the leaks that brought Sony Pictures to its knees over "The Interview," a movie satirizing the death of Kim Jong Un.
An FBI statement released Friday morning cites similar attacks against South Korean banks as part of the agency's assertion the group calling itself Guardians of Peace (GOP) was indeed sponsored by the hermit kingdom.
GOP brought down thousands of Sony computers, leaked hundreds of thousands of emails and made terror threats against movie theaters in an effort to keep the studio from releasing the movie.
At one point, the studio had to take its entire network offline, according to the feds.
"The FBI now has enough information to conclude that the North Korean government is responsible for these actions," reads the statement.
Agents determined the malware used to execute the hacks was previously used by North Korean hackers, right down to lines of code, encryption algorithms, data deletion methods and even compromised networks.
IP addresses linked to previous malicious actions by North Korea were also traced to the originators of the Sony attack, the agency said.
The hackers also used tools similar to those employed against Sony in a March cyber attack against South Korean banks and media outlets, investigators found.
"We are deeply concerned about the destructive nature of this attack on a private sector entity and the ordinary citizens who worked there," said the FBI.
"The destructive nature of this attack, coupled with its coercive nature, sets it apart. 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 agency vowed to work with international partners to bring those responsible for the attack to justice. Previous reports have suggested the crimes would be referred to an international criminal court.
China immediately called for any evidence the North Koreans were involved to be presented at the Chinese Embassy, in Washington, D.C.