U.S. government concludes cyber attack caused Ukraine power outage

WASHINGTON (Reuters) - A December power outage in Ukraine affecting 225,000 customers was the result of a cyber attack, the U.S. Department of Homeland Security said Thursday, marking the first time the U.S. government officially recognised the blackout as caused by a malicious hack.

Security experts had already widely concluded that the downing of utilities in western Ukraine on Dec. 23 was due to an attack, which is believed to be the first known successful cyber intrusion to knock a power grid offline.