Introduction

As you are probably already aware, the realm of security problems is large, varied, and rapidly changing. Nessus success in this realm is a result of its extensively configurable design and its large, varied, and easily augmented library of scanning modules. Nessus is the Swiss Army knife of network scanners. It can be used as a scalpel, as an axe, or as anything in between. It can provide a broad, bird s-eye view of a network, locate specific types of systems, investigate a particular service, or (if used without care) bludgeon the networked systems into complete collapse. The key to using the Nessus scanner safely and effectively is understanding the available options and how they can impact your network.

This chapter walks you through the process of planning, configuring, and running your first Nessus scan. Even if you already have experience using the Nessus scanner, this chapter might still provide insight about the different configuration choices and how you can use them to improve your scan results.

Effective use of Nessus requires careful planning beforehand. The user should have a clear goal in mind and make use of all available information to refine the scanning approach (goal and approach to be refined at each step). In this chapter, we assume that you are scanning an isolated test network or a well-known subnet of your real network. Recommended settings for your first scan are provided in the Solutions Fast Track section at the end of this chapter. We will discuss...