Attacks on federal facilities in the U.S. have highlighted the need to identify lessons learned from prior security incidents and apply that knowledge to security procedures government-wide. Dozens of federal law enforcement agencies provide physical security services for domestic non-military federal facilities. The Interagency Security Committee (ISC) is responsible for developing government-wide physical security standards and co-ordinating agencies to improve the protection of federal facilities. This book examines the practices used to identify and apply lessons learned and how agencies have used these practices; the actions the ISC has taken to identify and apply lessons learned from attacks on federal facilities; and the challenges to developing a government-wide lessons learned process and the strategies agencies have used to mitigate those challenges. The Government Accountability Office (GAO) has reviewed documents and interviewed officials from 35 security and law enforcement agencies with experience protecting selected tourist sites in cities in Greece, Israel, Italy and the United States.