Think your PC is protected by those passwords you key in every time you start up or log on to your e-mail client or Web applications? Think again. As Kevin Mitnick, the world's most famous hacker, told reporters after his release from federal prison, computer passwords are almost useless.

But even if hackers fail to break your passwords, you still run the risk of someone tracking your online behavior, infecting your system with a virus, or, just for kicks, wiping out your entire hard drive. And what good is having all your data protected and encrypted on your hard drive if you send sensitive information in the clear via e-mail—or worse, IM?

Furthermore, all the passwords in the world won't help much if someone walks off with your notebook or PDA.

So to help you protect not only your PC and notebook but also your PDA from serious hackers, bored script kiddies, thieves, viruses, spyware, nosy employers, and even jealous spouses, we give you an all-encompassing overview of the computer security market. We review hardware and software security tools, including encryption tools, data erasers, firewalls, antivirus apps, surveillance devices, and spyware detectors, and delve into technologies you may never have thought of.

We take a look, for example, at steganography, a technique for hiding documents inside images and sound files. We examine the biometric devices—tools that take fingerprint or iris scans before allowing access. We even look at data bombs, applications that will wipe your PDA clean if it's stolen. Don't want to spend anything on extra security? Peruse the many free ways you can protect your machine.

There are more ways than you know for someone to steal your personal information and private data. Luckily, there are more ways to protect it, too.