Know-how for defending against hacker attacks. More security for networks, systems, and applications. A practical guide with a conceptual approach. Illustrated with timeless examples. A competition among hackers? Who can crack the security system the fastest? The other side - the security experts - must be able to understand computer networks, systems, and applications from an attacker's perspective in order to identify and efficiently close security gaps. This book supports them in that endeavor. The topic of security is approached pragmatically here. The security of a component often directly depends on one or more other components, with these dependencies being complex and difficult to grasp. Based on the experiences gathered during the Hacker Contest, the book provides practical insights into the principles of hacking and cracking, as well as fundamental attack concepts.