Since all software has the potential for security holes, it's important to install security fixes for packages as soon as they become available. This is the single most often offered piece of advice by security experts, and the single most often ignored piece of advice by novice administrators. Don't learn this lesson the hard way -- when your boxes have been rooted by a years-old backdoor because you neglected to keep patches up to date.

The debate over whether open source or closed-source software is more secure is a hotly debated one. The best conclusion that can be drawn to date is that they are both usually adequate when properly administered, which includes keeping security patches up to date!

Several Web sites can help you keep your software up to date, and keep you aware of known threats. These include the security-conscious CERT and SecurityFocus' BugTraq list, as well as your normal software update sites like freshmeat.net and your distribution's home page. We'll repeat these URLs also in Resources, but security is such an important issue that -- if you are not already familiar with these sites, we do recommend that you take a few minutes to visit the first two now.