What is hardening a computer system?

Answer 1

In essence - hardening a computer system means removing or shutting down everything on it that is not required for the intended operation and further configuring it to protect those connections and services that ARE required.

In more detail, "Hardening" a computer system refers to configuring the settings to protect it from threats. It includes things like turning on and configuring the host based firewall, encrypting the password file, setting network comminications to use encryption and authentication, blocking remote administration except through controlled channels. The purpose of system hardening is to eliminate as many security risks as possible. This typically includes removing all non-essential software programs and utilities from the computer. While these programs may offer useful features to the user, if they provide "back-door" access to the system, they must be removed during system hardening. The BIOS may be configured to prevent booting from anything but the local hard drive once the OS is installed and then secured with a password to prevent changes. Alternatively, the CD drive is listed as the first boot device, which enables the computer to start from a CD or DVD if needed. File and print sharing are turned off if not absolutely necessary and TCP/IP is often the only protocol installed. The guest account is disabled, the administrator account is renamed, and secure passwords are created for all user logins. Auditing is enabled to monitor unauthorized access attempts. The system may also be configured not to respond to "ping" requests. There are many other configuration settings that can be utilized to further secure the system.