TrueCrypt (Mac OS X 10.5 Leopard) 6.0

The ultimate freeware encryption program, TrueCrypt is loaded with powerful features that those concerned with protecting their data from thievery should want--and have.

It offers 11 algorithms for encrypting your private files in a password-protected volume. You can store your encrypted data in files (containers) or partitions (devices). TrueCrypt works hard to offer powerful data protection, recommending complex passwords, explaining the benefits of hidden volumes, and erasing telltale signs of the encryption process, including mouse movements and keystrokes. Though the interface may not be immediately intuitive, its powerful, on-the-fly encryption for no cost still earns the freeware security tool a top rating.

The useful tips in the extensive help manual and volume-creation wizard provide excellent guidance. In fact, they're required reading, as TrueCrypt lacks any considerable in-program help. For instance, the tutorial explains the entire concept beyond "hidden" volumes, but it doesn't quite explain how to mount them. One obvious downside of any strong encryption program is if you happen to forget your lengthy, secure password, you should consider any protected files as good as gone. However, once files are mounted to a local drive with your password or key, they conveniently behave just like any normal files, allowing you to easily open, copy, delete, or modify them another way. Dismount the volume, and voila--your previously accessible files are now safely secure from prying eyes.

Users can even create a hidden operating system, encrypted away from nosy busybodies, but make no mistake--TrueCrypt is not for the casual encryption explorer. Be sure to thoroughly understand what you're doing with the program before you do something regrettable.