Unix, and its cousins Linux and Mac OS X, were designed from day one to be multi-user systems. (For this posting I'll just call them collectively "Unix" systems.) To use such a system you must "log in" with a user name and password. When you do, you have access to only your own personal directory (folder) on the hard disk, plus a few "public" directories. All of the system files are protected from you, and this protection is enforced at the lowest level of the operating system. Only the administrator (normally called "root") can access the system files.

When you install your Unix system -- even though you're the system administrator -- you should set up a user account for yourself. Then you should log in as this "ordinary" user for all your day-to-day activities (web browsing, word processing, and the like). Because when you're logged in as "fred" (or whoever), nothing you or your programs can do can affect the system files! So if by chance (a) someone writes an effective Linux virus, and (b) you carelessly click on that attachment, all that can be damaged is your personal user files. You can't infect the operating system.

In contrast, when you set up a personal Windows system, you're basically running in Administrator mode all the time. You have permission to add and change system files -- DLLs, registry, the works -- and so a virus that you accidentally execute has those same permissions and can run rampant through your entire operating system.

This is why when you're using Unix, you should never log in as administrator unless this is absolutely required. For most admin tasks, like installing new software, you can log in temporarily as the administrator; and the system will prompt you when this is necessary. (And if you get such a prompt when you're not doing an administrative task, you know to be suspicious.)

If you're really paranoid, and have documents you don't want at the slightest risk of exposure to the Internet, create two user accounts for yourself. Use one of them for Internet activity, and the other for your "private" stuff. One user's files can be completely protected from another user, so your Internet persona can't access your private files any more than it can access the system files. (If you're going to do this, learn about how to set permissions for Unix files. By default, many systems allow users to read each other's files unless otherwise instructed.)

This is one reason why so few viruses have been written for Unix/Linux/Mac. It is so much harder to write an effective Unix virus, and Windows systems are so vulnerable -- and, truth be told, Windows systems are so much more numerous -- that most virus writers would rather go after the easy prey. Which is in turn one more reason why it's safer to use Unix.

"But," you say, "I must use Windows."

Okay, if your employer is requiring you to use Windows on your personal computer, you have my sympathy, and you'd best get to work on the other five lines of defense. If it's just that you need to use some software that's only available for Windows, you should investigate the many ways you can run that software under (or alongside) Linux. But if you're like the vast majority, who use PCs for web browsing, email, word processing, spreadsheets, and similar basic tasks, then Linux can easily meet your needs. (An average user needs Windows like a fish needs an Edsel.) Yes, you'll have to learn some new things, and yes, you'll have to undergo the nuisance of converting your files, but you have to ask yourself: "is the security of my computer and my data worth it?"

brad