..'.excellent for use as a text in information assurance or cyber-security courses...I strongly advocate that professors...examine this book with the intention of using it in their programs.' (Computing Reviews.com, March 22, 2007) 'The book is written as a student textbook, but it should be equally valuable for current practitioners...this book is a very worthwhile investment.' (Homeland Security Watch, August 17, 2006) While the emphasis is on the development of policies that lead to successful prevention of terrorist attacks on the nation's infrastructure, this book is the first scientific study of critical infrastructures and their protection. The book models the nation's most valuable physical assets and infrastructure sectors as networks of nodes and links. It then analyzes the network to identify vulnerabilities and risks in the sector combining network science, complexity theory, modeling and simulation, and risk analysis. The most critical components become the focus of deeper analysis and protection. This approach reduces the complex problem of protecting water supplies, energy pipelines, telecommunication stations, Internet and Web networks, and power grids to a much simpler problem of protecting a few critical nodes. The new edition incorporates a broader selection of ideas and sectors and moves the mathematical topics into several appendices.