Practical Internet and UNIX Security, (2nd edition of Practical UNIX Security), Simson Garfinkel and Gene Spafford (O'Reilly & Associates, late 1995 or early 1996). An excellent book-length treatment of system security and the associated system administrative concerns and tasks.

Essential System Administration, 2nd edition, Æleen Frisch (O'Reilly & Associates, 1995). A substantial chapter is devoted to system security, as are numerous additional sections throughout the book.

Firewalls and Internet Security, William R. Cheswick and Steven M. Bellovin, (Addison-Wesley, 1994); Building Internet Firewalls, D. Brent Chapman and Elizabeth D. Zwicky (O'Reilly & Associates, 1995). Two essential books for anyone considering setting up a firewall system.

Security Alerts Mailing Lists

The Computer Emergency Response Team (CERT) manages the primary UNIX-related security-alert system. Send email to cert-advisory-request@cert.org to be added to the mailing list. Past advisories and updates are available via anonymous ftp to info.cert.org:/pub/cert_advisories

There is also a Linux-specific security advisory mailing list. Send email to majordomo@linux.nrao.edu with subscribe linux-alert in the body of the message to be added to the list. You may also want to subscribe to the linux-security mailing list, which is a moderated discussion list for Linux-related security topics (to subscribe, include subscribe linux-security in the body of a message to the same e-mail address). The archives for these mailing lists are available via anonymous ftp to linux.nrao.edu:/pub/linux/security/list-archive.