As virtually every aspect of society becomes increasingly dependent on information and communications technology, so our vulnerability to attacks on this technology increases. This is a major theme of this collection of leading edge research papers. At the same time there is another side to this issue, which is if the technology can be used against society by the purveyors of malware etc., then technology may also be used positively in the pursuit of society's objectives. Specific topics in the collection include Cryptography and Steganography, Cyber Antagonism, Information Sharing Between Government and Industry as a Weapon, Terrorist Use of the Internet, War and Ethics in Cyberspace to name just a few. The papers in this book take a wide ranging look at the more important issues surrounding the use of information and communication technology as it applies to the security of vital systems that can have a major impact on the functionality of our society. This book includes leading contributions to research in this field from 9 different countries and an introduction to the subject by Professor Julie Ryan from George Washington University in the USA.