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Pedestrians walk past an exterior wall to Sony Pictures Studios in Los Angeles on Thursday, a day after Sony Pictures denounced a “brazen” cyber attack. Image Credit: AFP

LOS ANGELES: The FBI is investigating threatening emails sent to some employees of Sony Pictures Entertainment, which was hit by a cyberattack that disrupted its computer system and spewed confidential information onto the internet. The FBI was trying to identify the person or group responsible, the agency said in a statement. It did not provide any details.

However, the trade paper Variety said the email written in broken English claimed to be from the head of the GOP — short for Guardians of Peace — the same group that took credit for last week’s attack. The email warns employees: “Please sign your name to object the false of the company at the email address below if you don’t want to suffer damage. If you don’t, not only you but your family will be in danger.”

“Make your company behave wisely,” the email urges.

The Los Angeles Times reported the email was received on Friday. A Sony spokesman confirmed in an email to the Times that “some of our employees have received an email claiming to be from GOP” and said the company was working with law enforcement.

Employees were told to turn off their mobile devices after receiving the message, Variety said, citing Sony insiders it did not name.

Five movies, including the unreleased “Annie”, have shown up on file-sharing websites. On November 24, workers who logged onto Sony Pictures’ network saw a skeleton and the message “Hacked by #GOP”.

Some cybersecurity experts say they’ve found striking similarities between the code used in the hack of Sony Pictures Entertainment and attacks blamed on North Korea that targeted South Korean companies and government agencies last year.

Experts are divided, however, over the likelihood that North Korea or independent hackers were involved.