Sony Hacking Scandal -- Execs Convinced It's an Inside Job

Sony execs are now convinced someone who worked for the studio is behind the massive hacking ... because no one from the outside could so precisely target the compromising information.

Multiple sources connected to the studio tell TMZ ... the strong, prevailing view is that the North Koreans are probably involved, but they used someone with intimate knowledge of the Sony email system to laser in on the most embarrassing information.

We're told the people at Sony who are investigating believe the hackers had intimate knowledge of mail systems and their configurations. They also believe the hackers have knowledge of the internal media distribution systems and the internal IT systems, including human resources and payroll.