Introduction

In spite of the ups and downs of the dot-com industry, open source software has become a viable alternative to commercial companies such as Microsoft, Sun, and IBM. Although open source software has its quirks and its problems, the open source movement has made its niche in the networking market. As a networking professional, it is in your best interest to understand some of the more important security applications and services that are available.

This book is designed to provide experienced systems administrators with open source security tools. Although we have made every effort to include as many people and as many skill sets as possible, this book assumes a fundamental knowledge of Linux. This book focuses on open source Linux applications, daemons, and system fixes. In the book s first chapters, you will learn how to lock down your network. Chapter 2 discusses ways to secure and monitor the operating system, and ways to scan local and remote networks for weaknesses. You will receive detailed information on how to ensure that your system s services and the root account are as secure as possible.

In Chapter 3, you will learn how to deploy antivirus and scanning programs for your local system. By using these scanning programs, you will be able to mitigate risk and learn more about the nature of services on your network. Scanners such as nmap and nessus will help you learn about the open ports on your network, and how these open ports might pose a threat...