As part of this special issue on control systems for the energy sector, guest editors Sean Peisert and Jonathan Margulies put together a roundtable discussion so readers can learn about the security challenges facing the industrial control system/SCADA world from those who are on the front lines. The discussion touches on some of the hard problems of securing mission-critical systems in the real world, including the challenges of securing 20-year-old legacy infrastructures, defining vendors' roles and responsibilities in security, and where research and new technologies are needed to fill today's security gaps.