Practical UNIX and Internet Security, 3rd Edition

Unix “Security”?

When the first version of this book appeared in 1991, many people thought that the words “Unix security” were an oxymoron—two words that appeared to contradict each other, much like the words “jumbo shrimp” or “Congressional action.” After all, the ease with which a Unix guru could break into a system, seize control, and wreak havoc was legendary in the computer community. Some people couldn’t even imagine that a computer running Unix could ever be made secure.

Since then, the whole world of computers has changed. These days, many people regard Unix as a relatively secure operating system. While Unix was not originally designed with military-level security in mind, it was built both to withstand limited external attacks and to protect users from the accidental or malicious actions of other users on the system. Years of constant use and study have made the operating system even more secure, because most of the Unix security faults have been publicized and fixed. Today, Unix is used by millions of people and many thousands of organizations around the world, all without obvious major mishaps.

But the truth is, Unix really hasn’t become significantly more secure with its increased popularity. That’s because fundamental flaws still remain in the operating system’s design. The Unix superuser remains a single point of attack: any intruder or insider who can become the Unix superuser can take over the system, booby-trap its programs, and hold the computer’s users hostage—sometimes ...