This course discusses different types of malicious attacks and various methods of mitigating to them. Students learn how to protect computer networks by using security codes. Topics covered includes foundations of network security, IP packet structure and analysis control, routing and access control lists, attack techniques, network defense fundamentals, sign-on solutions and file encryption solutions. At the end, the course students will be able to understand the security problems introduced by the combination of the Internet with Intranets, mobile devices, and sensors networks. Students will also be able to develop a basic understanding of the theoretical and conceptual aspects that are needed to build secure systems.