“A faster way to securely delete files” by MalEbenSo of Mac OS X Hints describes how you can use Disk Utility to securely delete files faster than the Finder.
Mac OS X has a “Secure Empty Trash…” feature that erases your deleted files in a permanent manner that prevents anyone else from recovering them with forensic analysis. Not only is a file removed, but OS X overwrites the place on your hard disk in which that files was stored multiple times with new, meaningless data. This is meant to make your information more secure in the event that an unauthorized person obtains physical access to your computer, such as a thief stealing your Mac and using “undelete” software to grab your bank account numbers.
One down side of “Secure Empty Trash…” is that if you are impatient, OS X may drive you up the wall — it takes a very long time to complete this task. The author of “A faster way to securely delete files” used a different deletion method to speed things up. His method only overwrites the deleted files once so it is not as secure as using the time-intensive Finder operation, but he argues that in most cases it is “safe enough”.
