LOS ANGELES/WASHINGTON/BOSTON - Eight days after a massive cyber attack on Sony Pictures Entertainment, the Hollywood studio was still struggling to restore some systems on Tuesday evening as investigators combed for evidence to identify the culprit.
Some employees at the Sony Corp entertainment unit were given new computers to replace ones that had been attacked with the rare data-wiping virus, which had made their machines unable to operate, according to a person with knowledge of Sony's operations.
In a memo to staff seen by Reuters, studio co-chiefs Michael Lynton and Amy Pascal acknowledged that "a large amount of confidential Sony Pictures Entertainment data has been stolen by the cyber attackers, including personnel information and business documents."
They are "not yet sure of the full scope of information that the attackers have or might release," according to the memo first reported by Variety, and encouraged employees to take advantage of identity protection services being offered.
Their concern underscores the severity of the breach, which experts say is the first major attack on a US company to use a highly destructive class of malicious software that is designed to make computer networks unable to operate.
Government investigators led by the FBI are considering multiple suspects in the attack, including North Korea, according to a US national security official with knowledge of the investigation.
The FBI said Tuesday that it is working with its counterparts in Sony's home country of Japan in the investigation.
That comes after it warned US businesses on Monday about hackers' use of malicious software and suggested ways to defend themselves. The warning said some of the software used by the hackers had been compiled in Korean, but it did not discuss any possible connection to North Korea.
The hack, which was launched Nov. 24, only affected computers with Microsoft Corp's (MSFT.O: Quote, Profile, Research, Stock Buzz) Windows software, so Sony employees using Apple Inc (AAPL.O: Quote, Profile, Research, Stock Buzz) Macs, including many in the marketing department, had not been affected, according to the person familiar with Sony's operations, who was not authorised to publicly discuss the attack.
Sony Pictures Entertainment shut down its internal computer network last week to prevent the data-wiping software from causing further damage, forcing employees to use paper and pen.