Introduction

Understanding what cybercrime is and how cybercrimes can be committed gives an investigator only half the picture. Just as every police officer needs a good grasp of physical defensive tactics, the cybercrime investigator must be aware of the tactics that are commonly used to defend a network from criminal intrusion or attack. In this chapter, we discuss the basic concepts involved in computer and network security. This includes the importance of multilayered security and the components that make up a multilayered security plan. We also emphasize the need for investigators to “talk the talk” by learning computer security terminology.

We delve into the fascinating and complex world of cryptography, the study of “hidden writing.” We look at encryption technologies and algorithms and the many ways in which encryption can be used to protect data stored on computers or traveling across the network. You'll learn about the purposes of encryption in the context of network security and how it can provide for authentication, data confidentiality, and data integrity. We provide a brief history of cryptography and discuss common encryption protocols in use today. We also explain the differences between encryption and steganography and how these two techniques are used together for stronger security—by both the good guys and the cybercriminals. Finally, we discuss cryptanalysis and decryption techniques and how cryptographic software is being used today as a terrorist tool.