Computers now control even the largest pieces of industrial machinery, making critical infrastructure vulnerable to electronic attack. As David Nicol, director of the Information Trust Institute at the University of Illinois, Urbana-Champaign, describes in "Hacking the Lights Out", determined hackers could bring down a significant portion of the U.S. electrical grid. Yet the threat is not just theoretical. Over the past decade electronic intrusions have disrupted operations at power plants, sewage treatment centers and nuclear facilities. Here are some of the more notable break-ins.