As computers and other digital devices have become essential to business and commerce, they have also increasingly become a target for attacks. For a company or an individual to use a computing device with confidence, they must first be assured that the device is not compromised in any way and that all communications will be secure. This chapter reviews the fundamental concepts of information systems security and discusses some of the measures that can be taken to mitigate security threats. The chapter begins with an overview focusing on how organizations can stay secure. Several different measures that a company can take to improve security will be discussed. Finally, you will review a list of security precautions that individuals can take to secure their personal computing environment.