As stated by the FBI, some careless errors were made by the hackers. The hackers regularly used a proxy system to conceal their actual place but in several instances posted and signed into a Sony server without concealing their place. The FBI says the hackers’ address is understood to be only used by North Korea.

“We still do not have all of the evidence and all the advice that is backing his powerful claim there,” Zetter says.

Some things that give pause to Zetter:

We do not understand what this IP address linked to or what it is.
How can we realize that?
First communication from the hackers never mentioned the film “The Interview.” It seemed to be an extortion effort to get cash out of Sony.
The FBI has requested that advice is unclassified by the government associated with the case that more can be freely revealed.

They’re are working on replacing gear and still fighting.