This work is intended to be of interest to counter-terrorism experts and professionals, to academic researchers in information systems, computer science, political science and public policy, and to graduate students in these areas. The goal of this book is to highlight several aspects of patrolling the Web that were raised and discussed by experts from different disciplines. The book includes academic studies from related technical fields, namely, computer science and information technology, the strategic point of view as presented by intelligence experts, and finally the practical point of view by experts from related industry describing lessons learned from practical efforts to tackle these problems. This volume is organized into four major parts: definition and analysis of the subject, data-mining techniques for terrorism informatics, other theoretical methods to detect terrorists on the Web, and practical relevant industrial experience on patrolling the Web.