FBI Accuses North Korean Government in Cyberattack on Sony Pictures

I guess this is the authoritative determination, despite the extant doubts that Pyongyang is behind the hack.

At NYT, "Obama Vows U.S. Response to North Korea Cyberattack on Sony":

In describing the United States’ evidence against North Korea, the F.B.I. said that there were significant “similarities in specific lines of code, encryption algorithms, data deletion methods, and compromised networks” to previous attacks by the North Koreans. It also said that there were classified elements of the evidence against the North that it could not reveal.

“The F.B.I. also observed significant overlap between the infrastructure used in this attack and other malicious cyberactivity the U.S. government has previously linked directly to North Korea,” the bureau said. “For example, the F.B.I. discovered that several Internet protocol addresses associated with known North Korean infrastructure communicated with I.P. addresses that were hard-coded into the data deletion malware used in this attack.”

The F.B.I. said that some of the methods employed in the Sony attack were similar to ones that were used by the North Koreans against South Korean banks and news media outlets in 2013.

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

It added: “Though the F.B.I. has seen a wide variety and increasing number of cyberintrusions, 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. Such acts of intimidation fall outside the bounds of acceptable state behavior.”

The F.B.I.'s announcement was carefully coordinated with the White House and reflected the intensity of the investigation; just a week ago a senior F.B.I. official said he could not say whether North Korea was responsible. But it also puts new pressure on President Obama on how to respond. Administration officials note that the White House has now described the action against Sony as an “attack,” as opposed to mere theft of intellectual property, and that suggests that Mr. Obama is now looking for a government response, rather than a corporate one.

Also, at the FBI's homepage, "Update on Sony Investigation."