The books described below are my personal "working set" of references on Internet administration topics. They cover topics that should be of interest to any administrator of an Internet-linked UNIX machine. The topics covered range from basic networking lore through issues of privacy and security.

Basics

Essential System Administration, 2nd. Ed.
AEleen Frisch
O'Reilly, 1995, ISBN 1-56592-127-5

Interconnections
Bridges and Routers
Radia Perlman
Addison-Wesley, 1992, ISBN 0-201-56332-0

UNIX System Administration Handbook, 2nd. Ed.
Evi Nemeth, et al.
Prentice Hall, 1995, ISBN 0-13-151051-7

UNIX Internetworking, 2nd. Ed.
Uday O. Pabrai
Artech House Publishers, 1996, ISBN 0-89006-778-3

Neither Essential System Administration nor UNIX System Administration Handbook spends much space on Internet-related topics. On the other hand, good system administration is a necessary part of good Internet administration. Along with lots of useful information, the Handbook includes a CD-ROM of useful freeware. Sources are included, as well as binaries for BSDI, HP-UX, IRIX, OSF/1, Solaris, and SunOS.

UNIX Internetworking covers the range from network-related UNIX system administration through moderately arcane networking lore. The book's clear exposition and logical organization make it a solid introductory or reference work.

Interconnections is an excellent introduction to the world of bridges and routers. It is readable, authoritative, and well organized. If your site contains more than a dozen machines, you probably need this book.

HTML, etc.

How to Set Up and Maintain a World Wide Web Site
The Guide for Information Providers
Lincoln D. Stein
Addison-Wesley, 1995, ISBN 0-201-63389-2

HTML for Fun and Profit
Mary E. S. Morris
Prentice Hall, 1995, ISBN 0-13-359290-1

HTML Sourcebook
A Complete Guide to HTML
Ian S. Graham
Wiley, 1995, ISBN 0-13-359290-1

There are dozens, if not hundreds of books on HTML and the Web. Most, however, are pretty fluffy. These three books, fortunately, are not.

How to Set Up and Maintain a World Wide Web Site covers a great deal of useful material. I wish I had had a copy when I was setting up my own site; I certainly keep my copy nearby these days!

HTML for Fun and Profit is a clear introduction to HTML, with frequent useful diversions into Perl-based CGI scripting. HTML Sourcebook is more useful as a reference to HTML and related tools.

Privacy

Applied Cryptography, 2nd. Ed.
Protocols, Algorithms, and Source Code in C
Bruce Schneier
Wiley, 1995, ISBN 0-471-11709-9

PGP
Pretty Good Privacy
Simson Garfinkel
O'Reilly, 1995, ISBN 1-56592-098-8

Protect Your Privacy
A Guide for PGP Users
William Stallings
Prentice Hall, 1995, ISBN 0-13-185596-4

The Internet is not a safe way to transmit sensitive information. Each packet typically passes through dozens of other sites. If any of the gateway machines are compromised, the packet is open to inspection and/or modification.

The perpetrators could be the oft-mentioned crackers, who range from idly curious to actively malicious. Alternatively, they could be commercial or government employees. Aided by ever-faster machines, there is very little constraint on the amount of snooping these folks can do. Clearly, some amount of caution is advisable.

Although cryptography is not a perfect answer, it can provide significant benefits at a minimal cost. Properly encrypted messages are safe from almost anyone's scrutiny, at least for the present. In addition, messages can be signed, preventing both forgery and unauthorized modifications.

Applied Cryptography is the obvious starting point for anyone who wants to know more about cryptography. The explanations start out informally, then proceed to spell things out in detail. The supplied source code allows curious programmers to experiment with alternative strategies and implementations.

Once you have an idea of what cryptography can do for you, pick up a copy of PGP (Pretty Good Privacy). PGP is a popular (except with the NSA :-) set of tools for performing the usual range of cryptographic functions. Either of the PGP references above is fine; I'd get both.

Security

Building Internet Firewalls
D. Brent Chapman and Elizabeth D. Zwicky
O'Reilly, 1995, ISBN 1-56592-124-0

Computers Under Attack
Intruders, Worms, and Viruses
Peter J. Denning, ed.
Addison-Wesley, 1990, ISBN 0-201-53067-8

Practical UNIX Security
Simson Garfinkel and Gene Spafford
O'Reilly, 1991, ISBN 0-937175-72-2

The same set of bad guys that snoop your packets on the Internet may come calling at your site. If they get in, they could cause considerable damage. Fortunately, there are ways to stop or at least discourage them.

Read Computers Under Attack to find out what kinds of threats you may encounter. Next, read Practical UNIX Security to find out what kind of precautions you can take to tighten up your local systems.

Finally, and most critically, read Building Internet Firewalls. UNIX is too accomodating and complex to be really secure. Thus, there is only a limited amount of protection you can achieve by installing patches and tightening up permissions. And, realistically, there is only so much internal security your users will tolerate.

By setting up an appropriate firewall, however, you can keep most intruders outside of your most sensitive areas. You'll still have to worry about incautious or even malicious employees, but their numbers are smaller, so you have a better chance to catch and/or discourage them.