In the last decade, the proliferation of billions of new Internet-enabled devices and users has significantly expanded concerns about cybersecurity. How much should we worry about cyber threats and their impact on our lives, society, and international affairs? Are these security concerns real, exaggerated or just poorly understood? In this fully revised and updated second edition of their popular text, Damien Van Puyvelde and Aaron F. Brantly provide a cutting-edge introduction to the key concepts, controversies and policy debates in cybersecurity today. Exploring the interactions of individuals, groups and states in cyberspace, and the integrated security risks to which these give rise, they examine cyberspace as a complex socio-technical-economic domain that fosters both great potential and peril. Structured around ten chapters, the book explores the complexities and challenges of cybersecurity using new case studies - such as NotPetya and Colonial Pipeline - to highlight the evolution of attacks that can exploit and damage individual systems and critical infrastructures. This edition includes new pedagogical features such as "reader's guides" and active-learning exercises, in addition to questions for group discussion. Cybersecurity is essential reading for anyone interested in understanding the challenges and opportunities presented by the continued expansion of cyberspace.