Attacks on computer systems have become part of everyday life. It is the goal of this class to teach a basic understanding of the possible security failures, as well as the protection mechanism. The class will cover an introduction to network and host security concepts and mechanisms; basic cryptographic algorithms and protocols; authentication and authorization protocols; access control models; common network (wired and wireless) attacks; typical protection approaches, including firewalls and intrustion detection systems; and operating systems and application vulnerabilites, exploits, and countermeasures. The class is designed for undergraduate, master's, and Ph.D. students. Those who take the class are expected to be able to program in C, have some basic knowledge of assembly language, and be familiar with network programming, as well as Unix-like operating systems.