The December 23, the national power grid of Ukraine suffered a cyber-attack that caused a blackout for several hours, which resulted in more than 600.000 of homes in the Ivano-Frankivsk region going dark. The attack would have been made using the Trojan BlackEnergy and social engineering. It would be the first time in history that a computer attack caused power outage.
Update 12/02/2016: U.S. official accuses Russia of the Ukrainian power plant attack.
Update 03/03/2016: Added information about the incident.