No surprises here. Ultimately the Norks are behind it, but I never thought it was a domestic Nork hacker team. My first guess was the Chinese and my second guess was the Russians. Both are known for massive hacker activity and they had the knowledge and ability to do it while I very much doubt any Nork team would.
The Norks just hired it out to the best hacker teams of which they knew.
I’ve always wondered why people refuse to believe that it was disgruntled former and/or current employees of the Sony IT department.