As the plot thickens, the "Whodunnit?" mystery behind the hacking of Sony Pictures Entertainment seems to be getting more and more complicated.

Theories of North Korea allegedly "contracting out" the cyber attack to another country are creating a buzz. Meanwhile, the FBI continues to stick to its stand of North Korea being the culprit and has refused to acknowledge the possibility that the hacking of Sony Pictures could be an inside job.

CNN has cited sources in the FBI who say the agency continues to be unrelenting despite seeing proof from data scientists, which point toward individuals who may likely be the perpetrators of the attack.

The report also said that data scientists from U.S. cyber security firm Norse and officials from the FBI met on Monday, Dec. 29, in St. Louis. The meeting lasted three hours and was initiated by Norse.

Norse's senior vice president Kurt Stammberger let on that during the meeting, the security firm's representatives disclosed evidence that links plenty of people to the hacking, including an ex-Sony employee. The said employee was with Sony in Los Angeles for 10 years before he was laid off in May this year.

Stammberger also revealed that the security firm has information on the malware samples, which suggest that only an insider from Sony could have access to the "super, super detailed insider information."

A blog post on Norse's site reveals that the company focused its search on a group of six people, which include an American, as well as people from Thailand, Singapore and Canada. Whether these individuals form the GOP is unclear at this juncture.

"An investigation into the massive breach at Sony has focused on a group of at least six individuals that may have worked to compromise the company's networks, including at least one ex-employee who had the technical background and system knowledge to carry out the attack," reads the blog post.

Norse also let on that the FBI was "grateful for the assistance" and "very open" to receive the data. The FBI has apparently been unable to share any of its data with the security firm owing to the "sensitivity of sources/techniques."

However, despite the new development, the FBI is unwavering in its theory that North Korea was behind the attack. This theory is based on data "from the FBI, the U.S. intelligence community, the DHS, foreign partners and the private sector."

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