Sony Pictures Entertainment has made progress getting its systems back online, after a hacker group hijacked networks last week, according to a person familiar with the matter.
The studio, which is behind movies such as "The Amazing Spider-Man" and TV shows including "The Blacklist," has also hired Mandiant, a forensics unit of the security firm FireEye, to investigate the incident, this person said. The Federal Bureau of Investigation is also looking into the matter.
On Monday, systems critical to business were back online, and the studio's email system was expected to get back up and running as well, this person said.
"Sony Pictures continues to work through issues related to what was clearly a cyber attack last week," the studio said in a statement. "The company has restored a number of important services to ensure ongoing business continuity and is working closely with law enforcement officials to investigate the matter."
Sony employees were locked out of the computer systems on Nov. 24, after they were infiltrated by a group calling itself GOP, or Guardians of Peace. The group claimed to have obtained "secrets" and threatened to release troves of data if its unspecified demands were not met.
Sony representatives have largely declined to comment on the scale of the attack.
In the days after the attack, pirated DVD copies of some Sony movies began to appear online on file sharing websites. A source said last week's system breach and the theft of the new movies were most likely related.
Among the titles that have popped up are the Brad Pitt World War II drama "Fury," the musical remake "Annie" and the upcoming film "Still Alice." Copies of "Mr. Turner" and "To Write Love on Her Arms" have also surfaced.
"The theft of Sony Pictures Entertainment content is a criminal matter, and we are working closely with law enforcement to address it," Sony said in a statement.
Reuters first reported the involvement of FireEye and the FBI. Representatives for FireEye did not immediately respond to requests for comment.
The FBI has confirmed it is working on the case.
"The FBI is working with our interagency partners to investigate the recently reported cyber intrusion at Sony Pictures Entertainment," said FBI spokewoman Laura Eimiller in a statement. "The targeting of public and private sector computer networks remains a significant threat, and the FBI will continue to identify, pursue, and defeat individuals and groups who pose a threat in cyberspace.