Explore the fundamentals of security and network forensics in this introductory lecture covering key concepts such as layered systems, perimeter firewalls, compliance, various types of cyber threats, defense strategies, and network models. Gain insights into the Information Age, levels of security, ISAE 2702, and the importance of defense in depth. Learn about Trojan horses, worms, denial of service attacks, inference, cover channels, and active attacks through practical examples. Understand the significance of demilitarized zones, the OSI model, and the Internet model in network security. Delve into this comprehensive overview based on Prof Bill Buchanan's book "Introduction to Security and Network Forensics" to build a strong foundation in cybersecurity principles.