U. S. critical infrastructures, such as financial institutions, commercial buildings, and energy production and transmission facilities, are systems and assets, whether physical or virtual, vital to the nation’s security, economy, and public health and safety. To secure these systems and assets, federal policy and the National Infrastructure Protection Plan (NIPP) establish responsibilities for federal agencies designated as Sector-specific agencies (SSAs), including leading, facilitating, or supporting the security and resilience programs and associated activities of their designated critical infrastructure sectors. The objectives of this book are to determine the extent to which SSAs have identified the significance of cyber risks to their respective sectors’ networks and industrial control systems; taken actions to mitigate cyber risks within their respective sectors; collaborated across sectors to improve cybersecurity; and established performance metrics to monitor improvements in their respective sectors.