Following the attacks of September 11, 2001, many agencies within the federal government began restricting some of their publicly available geospatial data and information from such sources as the World Wide Web. As time passes, however, decisionmakers have begun to ask whether and how such information specifically helps potential attackers, including terrorists, to select U.S. homeland sites and prepare for better attacks. Under the direction of the National Geospatial-Intelligence Agency, researchers at the RAND Corporation sought to clarify how geospatial information can be exploited by attackers and what kinds of information might prove most valuable. After evaluating both the "supply" and "demand" of geospatial data and information and surveying hundreds of Web sites, they developed a framework of three steps--usefulness, uniqueness, and benefits and costs--for assessing the implications of making such information available. The research detailed in this book aims to assist decisionmakers tasked with the responsibility of choosing which geospatial information to make available and which to restrict. In addition, the researchers make general recommendations about how the federal government should proceed in developing a more comprehensive model with similar features of the framework presented here, as well as how the U.S. government should communicate with public- and private-sector decisionmakers tasked with comparable assessments at more-local levels.