Textbook in PDF format This book offers a practical and in-depth exploration of Open Source Intelligence (OSINT) tailored for cybersecurity professionals, digital investigators, and threat analysts. It guides readers through actionable methodologies across key OSINT domains, such as domain/IP tracking, phone and email intelligence, vulnerability assessments, and threat profiling, using real-world tools and case studies. With focused coverage on both Windows and Linux environments, as well as high-profile ransomware and data breach investigations, this book bridges offensive techniques with ethical, responsible analysis. The book also emphasizes the importance of structured reporting, helping readers transform raw data into impactful intelligence. By combining technical rigor with strategic communication, this book equips readers with the skills needed to conduct effective, legally sound, and result-driven OSINT investigations. Preface Domain URL, IP address, and image intelligence People and Phone Intelligence Gathering vulnerabilities from OS and applications Security evaluation of Windows OS Email and domain intelligence Security evaluation of Linux OS and apps Threat profiling ransomware Threat profiling data breaches Threat profiling attackers Writing OSINT reports Conclusion Index