This book demystifies and explains a subject that affects every one of us in our private lives and at work. Security is a practical discipline concerned with safeguarding lives, property, information, wealth, reputations, and social wellbeing. It is the basis of civilised society. People, businesses, and nations cannot thrive in its absence, whereas the right kind of security frees us to live fulfilling lives.But deciding what is needed, and then making it happen, is not easy. The threats to our security are complex and continually evolving, as criminals, hackers, terrorists, and hostile foreign states continually find new ways of staying one step ahead of us, their potential victims. At the same time, we are continually creating new vulnerabilities as we adopt new technologies and new ways of working. Those who do not understand the fundamentals of security, risk, and resilience open themselves, and those around them, to avoidable dangers, needless anxieties, and unnecessary costs. In