At least one former employee of Sony Corp. may have helped hackers orchestrate the cyberattack on the company's film and TV unit, according to security researcher Norse Corp.

The company narrowed the list of suspects to a group of six people, including at least one Sony veteran with the necessary technical background to carry out the attack, said Kurt Stammberger, senior vice president at Norse.

The company used Sony's leaked human-resources documents and cross-referenced the data with communications on hacker chat rooms and its own network of Web sensors, he said.