The FBI warned Monday that hackers are using malware to crash the hard drives of U.S. businesses, following a cyber attack that laid waste to the computer network of Sony Pictures Entertainment. An FBI spokesperson declined to say whether the same malicious software was used in the Sony hack, according to a Reuters report.

The FBI’s warning said that the malware is capable of overriding hard drives’ existing data once its installed, “which can make them inoperable,” and can even shut down entire networks. It is difficult and very costly to recover any drives affected by the malware, and sometimes impossible, the bureau warned.

A number of details about the malware was included in the FBI’s warning, which was distributed to security administrators at U.S. companies on Monday. Such “flash” warnings, while common, do not name the victim of the cyber attacks they describe.

Some cyber-security professionals have theorized that North Korea was behind the hack that overtook Sony’s network. Those hackers released several of Sony’s films, some of which have not yet been released to theaters, like the “Annie” remake, and others that have beeen recently released, including the WWII tank drama “Fury.”