Executives at Sony Pictures Entertainment feel that someone who worked for the studio is behind the massive hacking because no one from outside could so precisely target the compromising information.
According to sources, the hackers belong to North Korea and their team includes former Sony employees, reports tmz.com.
The strong prevailing view is that the North Koreans are probably involved, but they used someone with intimate knowledge of the Sony e-mail system to laser in on the most embarrassing information.
The investigators confirmed that the hackers had an intimate knowledge of mail systems and their configurations. There can be a possible link between the hackers and Sony layoffs, which included a large number of IT employees.