The rapid development in information technology during the last few decades has not only given us greater opportunities to freely search for information and contacts. The growth of the Internet has also created new opportunities for criminal organisations, political activists and terrorists to threaten individuals, companies and countries. Individuals and organisations are also increasingly the targets of attacks and espionage via the web. There are various kinds of illegitimate and criminal activities. Every modern state thus has to create strategies and courses of action in order to protect information, networks and computers that are vital to society from malicious cyber activities. Creating secure systems and minimising risks of information being leaked or tampered with should be a prioritised task. It is also important to understand what threats arise from the information technological revolution. The purpose of this book is to give a broad background to the development of the dark side of the internet and its consequences. It is not about scaremongering, but about creating understanding and knowledge and thus preparedness in order to handle detrimental activities. It describes the changes in progress and what they may mean to society, companies and individuals as well as to the military and police.