Sony hires Mandiant to clean up after cyber attack

Sony Pictures has hired FireEye's Mandiant forensics unit to clean up a massive cyber attack that knocked out the studio's computer network nearly a week ago.

Internal systems at the Sony division went down last Monday after displaying a red skull and the phrase "Hacked By #GOP".

Technicians are making headway in repairing damage caused by the attack and expect to have the email systems back online today, a source close to the matter said.

Sony executives have declined to comment on the scope of the attack, though emails have been bouncing back with messages asking senders to call employees because the system was "experiencing a disruption."

A representative with FireEye declined comment.

Mandiant is an incident response firm that helps victims of breaches identify the extent of attacks, clean up networks and restore systems.

Sony is reportedly investigating whether hackers working on behalf of North Korea might be responsible for the attack, according to Re/code -  possibly in retribution for the studio's backing of the film "The Interview," which is to be released on Dec. 25 in the United States and Canada.

The movie - a comedy about a CIA attempt to assassinate North Korean leader Kim Jong Un - has been denounced by the Pyongyang government as "undisguised sponsoring of terrorism, as well as an act of war".