Publisher Summary Unix systems are a large part of the equation. In the enterprise environment, it is not uncommon to have multiple Unix systems serving specific, individual purposes. All these systems, while often varying in platform and operating system type, are confronted with similar problems of insecure default configurations and newly discovered vulnerabilities, and they require work to maintain their integrity. This chapter begins with a brief discussion on attacking Unix and examines using information gathering attacks. This is followed with descriptions of common attacks used against Unix systems, such as exploiting programming errors and input validation errors. It explains the process of securely installing Unix, going through the steps necessary to obtain valid media, installing the host securely, and configuring the system to preserve host integrity. Features that can be used to make the host more secure, and takes a look at the integrity verification and securing of inherited systems are also examined in the chapter.