A US government investigation has concluded that North Korea is responsible for the hack of Sony Pictures and subsequent public dump of Sony emails, according to multiple news reports. The hack reportedly originated outside of North Korea, but per the country's orders. The hack appears to have been retaliation for The Interview, a Sony comedy that depicts the cartoonish assassination of North Korean leader Kim Jong Un. It's not yet clear what North Korean responsibility means for the movie's release, which was pulled after hackers threatened to attack the theaters, or whether there will be any US or Japanese policy response.

Why the Sony hack coming from North Korea matters

"US investigators have determined that the attack against Sony was the work of hackers working on behalf of the North Korean government," CNN's Evan Perez says. NBC News is reporting the same thing, adding that Pyongyang employed hackers outside of its borders to conduct the attack.

While North Koreas came under earlier suspicion, there were initially reasons to doubt whether it was responsible. Among other reasons, neither Sony nor the FBI had reported any evidence of North Korean culpability before the new investigation.

Assuming the US investigation is right, and also that North Korea was behind the terrorist threats on the film, this is a big deal. Yet it's still not clear why North Korea would do this. The country does have a history of lashing out to attract international attention and policy concessions.