Deployments of smart grids should be slowed until security vulnerabilities are addressed, according to some cybersecurity experts, citing tests showing that a hacker can cause a major blackout after breaking into a smart-grid system. The idea behind smart grids, a burgeoning energy sector in which even Google is playing a role, is that automated meters and two-way power consumption data can be used to improve the efficiency and reliability of an electrical system's power distribution. A washing machine in a household hooked up to a smart meter, for instance, could be set up to run only at lower-cost, off-peak hours,...