Practical UNIX & Internet Security

By Simson Garfinkel & Gene Spafford; ISBN 1-56592-148-8, 1004 pages.
Second Edition, April 1996.

In today's world of international networks and electronic commerce, every computer system is a potential target. Rarely does a month go by without news of some major network or organization having its computers penetrated by unknown computer criminals. Although some computer "hackers" (see the sidebar below) have said that such intrusions are merely teenage pranks or fun and games, these intrusions have become more sinister in recent years: computers have been rendered inoperable; records have been surreptitiously altered; software has been replaced with secret "back doors" in place; proprietary information has been copied without authorization; and millions of passwords have been captured from unsuspecting users.

Even if nothing is removed or altered, system administrators must often spend hours or days reloading and reconfiguring a compromised system to regain some level of confidence in the system's integrity. There is no way to know the motives of an intruder and the worst must be assumed. People who break into systems simply to "look around" do real damage, even if they do not read confidential mail and do not delete any files. If computer security was once the subject of fun and games, those days have long since passed.

Many different kinds of people break into computer systems. Some people - perhaps the most widely publicized - are the equivalent of reckless teenagers out on electronic joy rides. Like youths who "borrow" fast cars, their main goal isn't necessarily to do damage, but to have what they consider to be a good time. Others are far more dangerous: some people who compromise system security are sociopaths, joyriding around the networks bent on inflicting damage on unsuspecting computer systems. Others see themselves at "war" with rival hackers; woe to innocent users and systems who happen to get in the way of cyberspace "drive-by shootings!" Still others are out for valuable corporate information, which they hope to resell for profit. There are also elements of organized crime, spies and saboteurs motivated by both greed and politics, terrorists, and single-minded anarchists using computers and networks.

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