Since May, unidentified hackers have been breaking into computer networks of companies that operate American nuclear power stations, energy facilities and manufacturing plants, a report says.

The Department of Homeland Security and the Federal Bureau of Investigation issued a statement last week that confirmed the cyberattacks, The New York Times reported on Thursday.
Among the companies targeted was the Kansas based Wolf Creek Nuclear Operating Corporation, the report said.
More details of the cyberattacks were not immediately provided, and the severity of the attacks remains unclear, as does the motive for them.
The joint report, which was released on June 28, did not show whether the attacks were an effort at espionage or part of a plan to cause destruction or if hackers were looking to steal trade secrets.
The report indicated that “there is no indication hackers had been able to jump from their victims’ computers into the control systems of the facilities,” according to The Times. 
The newspaper obtained the report and got it confirmed from security specialists who have been dealing with the attacks.