Freedom and Information: Assessing Publicly Available Data Regarding U.S. Transportation Infrastructure Security, August 8, 2007: “This report concerns the feasibility of obtaining information relevant to planning terrorist attacks from publicly available sources. To the extent that such information is available, it is particularly valuable to terrorist planners in that it can generally be obtained at lower cost, risk, and effort than more direct forms of gathering information such as observation of a potential target. Familiarity with public sources of information is also valuable to defenders. If they are unaware that a terrorist group knows or can easily learn about a particular vulnerability, that vulnerability can be exploited more easily.”