Chapter 2: The X Window System

---

We know what you’re thinking: “How is the X Window System (or just X) a security tool?” You’re right in posing this question, because X isn’t a security tool. However, many graphical Unix tools mentioned in this book require that you install, configure, and use an implementation of X. For that reason, a brief description of X is provided here to show you how it works and how to secure it. The installation and configuration options are extensive and beyond the scope of this book, but we’ll aim to give you a general understanding of what’s going on in X. We’ll also touch on some inherent security concerns with X.

Choosing a Window Manager

A small but important detail about X is that it doesn’t come with a window manager or Desktop by default. X handles your keyboard, mouse, and output screen. It comes with a basic system that lets you “place” windows in locations on the screen and then terminate those windows. The fancy menus and toolbars are the domain of the window managers that run on top of X. Several window managers and desktops are available, including the popular Gnome, KDE, and Window Maker applications. It’s important for you to remember that X is only the underlying architecture for the windowing system; it has nothing to do with the look and feel of that graphical environment.

---