Time was, outages on the power grid were the result of downed tree limbs. Trees and branches are still an issue, but power companies increasingly are worried about hackers and computer viruses. To wit, the ominously named malware Black Energy took out a grid in Ukraine in 2015 and caused 800,000 people to lose power. The threat is only increasing — year over year, cyberattacks on industrial control systems have increased by 55 percent.