Industrial control systems (ICS) face daily cyber security threats, can have a significant impact to the security of our nation, and present a difficult challenge to defend. Critical infrastructures, including military systems like the machinery control systems (MCS) found on board modern U.S. warships, are affected because of their use of commercial automation solutions. The increase of automated control systems within the U.S. Navy saves in manpower costs but increases the need for cyber security research and defense. Research is needed to assess and contribute solutions to ICS security problems. This book describes the MCS security testbed, which supports research in the security of shipboard machinery control systems. The testbed has been conceptualized, designed and implemented with the vision of supporting research and experimentation on the defense of ICS and MCS systems. The testbed provides the ability to analyze vulnerabilities, test defenses and replicate attacks on authentic physical industrial control equipment. The MCS security testbed is a tool that may help counter cyber security threats facing the defense industrial base today. Future solutions to attacks on control systems in the nation's critical infrastructure begin with experimentation using authentic test environments.