The FBI is so determined to keep the fiction of North Korea being behind the Sony Pictures hack that they did something long unthinkable. They released part of the “evidence” underpinning the claim.
The FBI insisted that some of the emails sent to Sony executives were sent without using a proxy server, and subsequently their “real” IP addresses were believed to have been exposed, and were associated with North Korea.
The security experts doubt the claim, however, saying on the one hand that it is unlikely the hackers suddenly forgot about proxy servers, and doubly unlikely that the IP addresses, even if they were confirmed, could really be conclusively attached to North Korea.
An equally likely possibility is that the IP addresses the FBI is attributing to the hack are themselves proxies, and that the hackers simply hijacked the same addresses as previous attacks that the FBI also tried to pin on North Korea, giving the bureau an excuse to believe what they wanted to believe all along.