From my friend Alexis Kayhill on Mac360:
Here’s a little known and less understood fact of using a Mac (or a Windows PC). Emptying the trash (or the stupid recycle bin) doesn’t really delete files.
What about Secure Empty Trash in the Finder menu?
Secure Empty Trash merely overwrites the data seven times, according to some U.S. Department of Defense standard. And we all know how good those guys are at protecting data.
Here, here! Is there a better way, oh great Value Vixen™ of Southern California?
If you’re really paranoid about deleting the data on your Mac, and your whole world would collapse and you’d have to go into a Witness Protection Program of some sort if anyone ever found those secret files, then you need Permanent Eraser. First, it really, really scrambles the data you’re trying to erase. Not seven times. Not 20 times. But 35 times.
Permanent Eraser is free and also erases CD-RWs and DVD-RWs. Typically superb Mac utility. One click or drag and drop and you’re done.