Building Secure Servers with Linux

Other Handy Tools

SSH can help secure a truly staggering variety of administrative tasks. I’d be remiss, however, not to mention two other tools useful for this purpose. These tools, su and sudo , can help minimize the time you spend logged on as or operating with root privileges.

What’s Wrong with Being root?

Many new Linux users, possibly because they often run single-user systems, fall into the habit of frequently logging in as root. But it’s bad practice to log in as root in any context other than direct console access (and even then it’s a bad habit to get into, since it will be harder to resist in other contexts). There are several reasons why this is so:

Eavesdroppers

Although the whole point of SSH is to make eavesdropping unfeasible, if not impossible, there have been a couple of nearly feasible man-in-the-middle attacks over the years. Never assume you’re invincible: if some day someone finds some subtle flaw in the SSH protocol or software you’re using and successfully reconstructs one of your sessions, you’ll feel pretty stupid if in that session you logged in as root and unknowingly exposing your superuser password, simply in order to do something trivial like browsing apache logs.

Operator error

In the hyperabbreviated world of Unix, typing errors can be deadly. The less time you spend logged in as root, the less likely you’ll accidentally erase an entire volume by typing one too many forward slashes in an rm command.

Local attackers

This book is about bastion hosts, which ...