It is my pleasure to present this volume on Cyber Security, a vital and rapidly evolving field that underpins the safety of our digital society. As cyber threats grow in scale and complexity, understanding the principles, technologies, and practices that protect information systems is crucial for individuals, organizations, and governments. This book guides readers from beginners to experts through core concepts, threats, defenses, and the ecosystem of tools, laws, and strategies shaping modern security. Topics include network protection, application security, cloud defenses, IoT challenges, legal and ethical issues, and cyber incident response. Combining theory with practical insights, real-world examples, and best practices, it meets the needs of students, IT professionals, and business leaders. As an Associate Professor at Poornima University, I see the rising demand for accessible yet rigorous cybersecurity education. This work offers a clear roadmap, making it an invaluable resource for academia, industry, and self-learners, fostering awareness, skills, and collaboration to secure our digital future.