U.S. helping Ukraine investigate December power grid hack

By Dustin Volz WASHINGTON (Reuters) - The U.S. Department of Homeland Security said on Tuesday it was helping Ukrainian authorities investigate an apparent attack last month on the country's power grid that caused a blackout for 80,000 customers of western Ukraine's Prykarpattyaoblenergo utility. Experts have widely described the Dec. 23 incident as the first known power outage caused by a cyber attack.