A friend showed me how she can recover deleted files on her Mac OS X system using some utility or the other and it got me to thinking… how do I delete files on my own Mac so that she – or anyone else – can’t recover them later?
Dave’s Answer:
The Patriot Act requires me asking whether you want to securely delete files to prevent authorized law enforcement officials from their legal investigations?
Just kidding. I don’t really care what you’re deleting. 
Turns out that the Mac OS X system supports a very slick secure delete that can be easily enabled any time you feel like you might have snoops poking around your ex files, whether legitimately or not. Further, you can also just securely delete your trash when you have something particularly sensitive to delete, and otherwise leave it as a standard (e.g. recoverable) deletion.
First off, a secure deletion is one where the file system actually writes garbage over the existing contents of your file as part of teh deletion. Even if you dig around in the file system itself to find where the file was, the data’s gone. A normal deletion, by contrast, simply frees up the pointer to the file contents, while leaving the actual contents untouched until another file overwrites it, which could happen in a few seconds or not for a week.
Let me go backwards and start by showing you how to securely delete what’s currently in your trash. The easiest way is to look at the options on the “Finder” menu:
You can see that right below the usual “Empty Trash…” is “Secure Empty Trash…”. Choose that, and:
Notice the slightly different wording in the warning message. If you really want to delete the trash ‘securely’, go for it.
Another way you can get to this if you don’t remember the menu option is to just double-click on the trash icon itself in the Dock. It opens and you’ll see something like this:
Click on “Empty Securely” and you’ve removed anything recoverable from your disk.
Finally, you might just want to do what I’ve done: set up your preferences to automatically make every delete a secure one. This can be done by clicking on Preferences… in the Finder, then clicking on the “Advanced” option. Now you’ll see this:
Secure deletion is one of the many ways that the Mac OS X system makes it easy to secure your data in this age of identity theft. Useful indeed.
