http://www.slate.com/articles/technology/bitwise/2015/01/sony_hacks_and_north_korea_why_the_cyber_attack_is_as_mysterious_as_ever.html

The Sony Pictures hack—whodunit? Everyone is certain it was either North Korea or not North Korea. Even as the United States imposes new sanctions on North Korea for allegedly hacking Sony Pictures, stealing 100 terabytes of data, and obliterating the movie studio’s internal systems (as I discussed in a previous piece), there remain serious questions as to who exactly was responsible.