When you normally delete your files in Mac OS X, the operating system is only forgetting where those particular files are placed, while the data still physically remains on the drive. Beginning with Mac OS 10.3, Apple enhanced its security by introducing the Secure Empty Trash feature, which follows the U.S. DoD pattern of overwriting data seven times.
Permanent Eraser provides an even stronger level of security by implementing the Gutmann Method. This utility overwrites your data thirty-five times, scrambles the original file name, and truncates the file size to nothing before Permanent Eraser finally unlinks it from the system. Once your data has been erased, it can no longer be read through traditional means.