The company freezes IT systems as hackers claim they are poised to disclose private files and warn it is “just a beginning”.
Sony Pictures has reportedly ordered workers not to use email or connect to its network after hackers threatened to reveal “secrets” to the world.
A source told Hollywood site Variety that employees had been told to turn off computers and disable Wi-Fi on mobile devices.
An ominous skeleton image is said to have appeared on computers on Monday morning, along with the warning “Hacked By #GOP”.
The picture was leaked via a Reddit thread, apparently by an employee of the company, and other inside sources are reported to have verified the image.
It warns this attack is “just a beginning” and threatens to release private company files “till our request be met”.
Workers have apparently been told it is possible the issue could take up to three weeks to resolve.
Sony was hit by a serious, high-profile hacking attack in 2011 when millions of names and passwords of PlayStation Network customers were exposed.
The network also ground to a halt in August when a denial of service attack stopped players going online.
Sky News contacted Sony Pictures for comment, but it has not yet responded.