Explore the history, theory, and practical applications of firewalls in this 19-minute introductory talk by former White Hat president Jessie Pease. Delve into the strengths, limitations, and various implementations of firewalls, covering topics such as packet filtering, stateful firewalls, and application-level gateways. Learn about firewall rules, access control lists, and where to position your firewall for optimal security. Participate in hands-on activities to reinforce your understanding, making this talk suitable for both beginners and experienced professionals interested in network security.