As our economy and our society grow increasingly dependent on cyberspace we are only just beginning to understand how vulnerable that dependency makes us to catastrophic failure. This book clarifies shows how the security methods we have designed for the physical world are futile in cyberspace. If we want effective cybersecurity we need to understand the real and different nature of cyberspace, and the decision makers and security professionals have to understand the laws and rules of cyberspace and why and how they work in cybersecurity. Victor Sheymov's comprehensive multi-disciplinary approach suggests a fundamentally new approach to security in cyberspace, using methods native to cyberspace, and his book lays out a foundation for an effective, feasible and reliable cybersecurity technology. This Revised Edition (November, 2013) book consists of four parts. Part I, Security, is a review of access security in the world of our physical space. This review shows the reasons why our efforts in access security historically have been reasonably effective. Part II, Cyberspace, examines the specific qualities of cyberspace. It explains the fundamental differences between physical and cyberspace, and how these differences are relevant to cybersecurity. Part III, Cybersecurity, shows that methods used in computer security for the last quarter of a century are fundamentally alien to cyberspace. It explains why our efforts to secure cyberspace so far have been completely ineffective. It introduces new approaches to cybersecurity based on methods that are native to cyberspace that can provide real security in cyberspace, as well as protect our critical infrastructure. The VCC method of communications enables building cybersecurity systems that render hacking attacks computationally infeasible. Furthermore, this method does not require intrusions in customer's information and systems. It provides security without violating customer's privacy or civil liberties. Part IV, just added, Coherent Defense of Large Sovereign Cyber Systems, analyzes the challenges of increased size, the protective role of Government, argues that cyber security does not require encroaching on privacy, that the Variable Cyber Coordinates (VCC) technology provides crucial data processing advantage, and stresses that active monitoring of attackers is more effective than passive monitoring of defenders.