Monitoring systems are on one network while systems that control reactor operations is on a separate network that's closed to the outside. Ginter suggested the same architecture for vehicles where separate computers are used for monitoring and for critical functions, such as brakes, acceleration or steering.
"If they're not connected, then the only thing you can hack over the network is the monitoring functions," Ginter said. "The safety critical functions continue to work."
Miller and Valasek are scheduled to present details of their work this week at the Defcon security conference in Las Vegas.
Sign up for CIO Asia eNewsletters.