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.
Super Eraser Pro for Mac - Remove Unwanted Objects and Scale Photo Smartly
Disc Eraser allows you to erase a rewritable disc.
Permanently delete sensitive data from your storage devices.
Delete all data stored on your iOS device.
BCWipe data wiping software enables you to permanently delete selected files so that they can never be recovered or undeleted.