The U.S. Federal Bureau of Investigation warned U.S. businesses that hackers have used malicious software to launch destructive attacks in the United States, following a devastating cyber attack last week at Sony Pictures Entertainment.
The five-page, confidential "flash" warning issued to businesses late on Monday provided some technical details about the malicious software that was used in the attack, though it did not name the victim.
An FBI spokesman declined comment when asked if the software had been used against the California-based unit of Sony Corp .
The FBI occasionally issues "flash" warnings to provide businesses with details about emerging cyber threats to help them defend against new types of attacks. It does not name the victims of those attacks in those reports.
The report said that the malware overrides data on hard drives of computers which can make them inoperable and shut down networks.
It is extremely difficult and costly, if not impossible, to recover hard drives that have been attacked with the malware, according to the report, which was distributed to security professionals at U.S. companies.
(Reporting by Jim Finkle)