UNIX System Security: A Guide for Users and System Administrators (Addison-Wesley Professional Computing

Because the UNIX system was originally designed by programmers for use by other programmers, it was used in an environment of open cooperation where security was of minimal concern. Now that its use has spread to universities, businesses, and government, the confidential and sensitive nature of the data stored on UNIX systems has made the security of these systems of paramount importance.
Despite all the technical papers and workshops on UNIX security, this book is unique. "UNIX System Security" is the first up-to-date source to provide the UNIX system user or administrator with the information needed to protect the data and system from unauthorized use. By following the procedures described in this book and making use of the C programs and shell scripts provided as examples, you can protect your UNIX system from most attackers.
The author begins by examining four high-profile breaches of UNIX security as illustrations of how a UNIX system can be attacked. He then provides the information necessary to protect against these forms of attack, and offers the tools that can be used to do so. Focusing on the most recent release of Berkeley and System V UNIX, and such vendor derivatives as SunOS and ULTRIX, the book gives information that can be applied to any version of UNIX since Seventh Edition.
Issues discussed include account and password security, securing the file system, encryption and authentication systems, TCP/IP network security, the Network Information Service (NIS), NFS, RFS, workstation security, terminals and modems, and UUCP. Other chapters describe how to respond if your system is attacked and how to develop a comprehensive security policy for your organization. The book also gives comprehensive lists of freely available security software, and publications and mailing lists dealing with UNIX security.