Introduction

Linux is capable of high-end security; however, the out-of-the-box configurations must be altered to meet the security needs of most businesses with an Internet presence. This chapter shows you the steps for securing a Linux system called hardening the server using both manual methods and open source security solutions. The hardening process focuses on the operating system, and is important regardless of the services offered by the server. The steps will vary slightly between services, such as e-mail and Hypertext Transfer Protocol (HTTP), but are essential for protecting any server that is connected to a network, especially the Internet. Hardening the operating system allows the server to operate efficiently and securely.

This chapter includes the essential steps an administrator must follow to harden a Unix system; specifically, a Red Hat Linux system. These steps include updating the system, disabling unnecessary services, locking down ports, logging, and maintenance. Open source programs allow administrators to automate these processes using Bastille, sudo, logging enhancers such as SWATCH, and antivirus software. Before you implement these programs, you should first understand how to harden a system manually.

Updating the Operating System

An operating system may contain many security vulnerabilities and software bugs when it is first released. Vendors, such as Red Hat, provide updates to the operating system to fix these vulnerabilities and bugs. In fact, many consulting firms recommend that companies do not purchase and implement new operating systems until the first update is available. In most cases, the first update will fix many...