SecretShredder

Files can remain on your Mac even after they have been deleted or moved to the trash. Indeed using techniques like magnetic force microscopy data can be retrieved even after your drive has been formatted.
The only sure way to delete files and clean up your free disk space ( where files previously moved to the trash may still lie ) is to overwrite them many times using well-known bit patterns so that they can never be recovered.
Using advanced techniques SecretShredder will clean your drive so that data never comes back.
Just drag files onto the dock icon.

Or type apple T to shred the trash, it's that simple.
What's new in this version:
Internet Shred Bug FixInternet Shredding ( cache, cookies, history and more)German Trash Shredding FixGerman Language ImprovementGutmann standard supportedShred each file upto 50 timesDoD 5220.22M speed enhancementsBetter French localization supportDock menu addedBlurring text fixedTrash shredded accross multiple volumesTrash icon updated after shredFile icons removed after shred