Sony Pictures has hired a team of investigators and forensics experts to find out the causes of a cyber attack that just over a week ago brought down the company computer systems.
The attack, which took place on 24th November, led the company to a decision to take down its computer network until the matter is resolved.
According to Reuters, email messages to the company have been bouncing back, asking senders to call the company because the system is experiencing disruption.
While Sony's executives have declined to comment on the matter, reports have found the attack is undergoing internal investigation.
Was it North Korea?
A re/code report has said that the motion picture studio is now investigating whether or not the attack has links to North Korea.
The suspected motivation is tied the studio's December release The Interview, a film in which the lead characters attempt to assassinate the North Korean leader Kim Jong Un.
The Pyongyang government has made its position on the film clear: in a letter to UN Secretary-General Ban Ki-moon, Pyongyang said the film was "undisguised sponsoring of terrorism, as well as an act of war".
While these reports suggest the likelihood of North Korea's involvement, others are keen to stress that the link so far has not properly been established, and the mystery group still needs investigation.
When the computers at Sony offices went down last week, the Los Angeles Times reported that beneath a red skull on their screen all users saw a message which read "Hacked by #GOP", which stands for Guardians of Peace.
According to a Variety report, whoever the group is, it is likely that its attack caused a significant leak of Sony films.
Since the attack at least four water-marked films have leaked online, and of these films all were either still running in US theatres or not yet released. This includes Fury, which now has been pirated more than 1.2 million times.
It is not clear precisely how many of these downloads are related to the attack compared with how many are related to the more general issue of piracy.
A Sony spokeswoman said: “The theft of Sony Pictures Entertainment content is a criminal matter, and we are working closely with law enforcement to address it”.
Sony has hired the incident response firm Mandiant Forensics to help it identify the extent of the attacks and clean up its computer systems.