Your Mac has two options when deleting the contents of your Trash bin. The normal method and the secure method. This post will show you how to set Trash to securely delete your files every time. The normal deletion method simply removes the pointers to the file on the index of your drive, the file is still there, your Mac doesn’t realise this and overwrites it as if it was an empty part of your disk, this is why your Mac can delete hundreds, if not thousands, or files in no time at all. The secure method will actually write over the 1′s and 0′s of the file, as a result the file is completely gone and can’t be recovered.
To set Trash to always delete files securely open Terminal located in Applications > Utilities and type the following and press enter after each line:
defaults write com.apple.finder EmptyTrashSecurely -bool true
This will set Trash to delete files securely. You will notice now that the Finder menu bar options has the normal empty method removed and the small button within Trash has changed as shown in the images below.
If you don’t like this change, you can revert it back to the original using the following commands. Each on a new line.
defaults write com.apple.finder EmptyTrashSecurely -bool false
Its only a simple change, however if you regularly empty your trash securely its simple little change that can save you a couple of seconds. I have tested this trick on OS 10.6, so should work on this and all above versions.