This report analyzes terrorist groups’ use of advanced information and communication technologies in efforts to plan, coordinate, and command their operations. It is one component of a larger study that examines terrorists’ use of technology, a critical arena in the war against terrorism. The goal of the investigation reported here is to identify which network technologies might be used to support the activities that terrorists must perform to conduct successful operations, understand terrorists’ decisions about when and under what conditions particular technologies will be used and determine the implications of these insights for efforts to combat terrorism.