“We also believe that this attack is contained.”

“While we experienced disruptions at some of our properties, operations at our affected properties have returned to normal, and the vast majority of our systems have been restored,” MGM CEO Bill Hornbuckle said in a Thursday letter to customers. In 2019, the Norwegian aluminum manufacturer Norsk Hydro suffered $70 million in losses after refusing to pay ransomware criminals. If so, it could be the costliest ransomware attack on record, said Brett Callow of the cybersecurity firm Emsisoft. The incident bore all the hallmarks of an extortionary ransomware attack, which MGM has not confirmed.