How to Secure Your Computer, Disks, and Portable Drives
Computer security is hard. Software, computer and network security are all ongoing battles between attacker and defender. And in many cases the attacker has an inherent advantage: He only has to find one network flaw, while the defender has to find and fix every flaw.
Bruce Schneier says Unfortunately, cryptography can't solve most computer-security problems. The one problem cryptography can solve is the security of data when it's not in use. Encrypting files, archives -- even entire disks -- is easy.