ABSTRACT
The ability to counter security threats requires an understanding of those threats, which is the objective of this chapter. This chapter focuses attention on a variety of threats to both computers and the networks to which they are connected. Security threats to be examined include password cracking, network scanning, viruses, worms, and techniques that are used to deny service to legitimate users, the latter categorized as denial-of-service attacks. Information presented in this chapter can be considered to form a foundation for additional security-related material presented in Chapter 9, which focuses on techniques that can be employed to enhance security. While Chapter 9 focuses on techniques that can be used to enhance security, those techniques are primarily oriented toward the protection of the router connected to a public network, as well as the use of router access lists and firewalls to filter different types of network traffic. To ensure that readers will understand how to counter each threat discussed in this chapter, this chapter will either directly note an applicable countermeasure or reference material presented in Chapter 9.
