Computers are awesome machines for storing data and precious files. However, we should keep in mind that there are security risks associated with the data stored on any computer hard drive — be it Mac or PC.

Though files on a Mac can be deleted via the trash can, it does not mean trashed and deleted files are removed from the computer’s directory. The normal deletion of files simply make space on the computer disk for for new files, which means those files can still be recovered, with application like Disk Drill. In most cases, trashing files is sufficient for regaining disk space, but if you’re concerned about sensitive files being recovered on your Mac, you need to take additional steps to ensure those files are securely overwritten.

This article covers the default method for securely deleting files, plus a review of two third-party applications that overwrite deleted files.

Secure Empty Trash

The default method for securely deleting files in your Mac’s trash can is to go to the Finder menubar and select “Secure Empty Trash” from the drop-down menu. Using this OS X built-in feature overrides the deleted file 7 times. This means it could take perhaps three to seven times longer than normal to empty the trash.

In Finder Preferences, you can also select to have all your files securely deleted when you empty the trash. However, it is a very slow process when your computer’s trash can is full of 100 megabytes or more of data.

With Secure Empty Trash, files are overwritten a single time — for example, with a long string of zeros – which should be sufficient for secure deletion. But having the files overwritten 7 times (which apparently is good enough for the US Department of Defense), or 35 times, will make it nearly impossible for any of the securely deleted data to be recovered. Thus keep in mind, when you delete files in this way, there is no way to recover such data.

Also note, if you use Time Machine on your Mac, files saved to that or any other backup are not automatically deleted when you trash and delete the latest version of the file. You will need to go into your backup hard drive and delete files from there as well.

Paper Shredder

If you’re a Mac power user, no doubt your computer’s trash can is constantly full with all sorts of files. Thus you may find it a hassle to use the Secure Empty Trash when you want to securely delete one or more files at a time. Paper Shredder comes in handy for quickly wiping out critical files when they are dropped onto the application.

You can keep the application in your Mac’s Dock and simply drop files onto it to activate the secure delete process. Paper Shredder four offers options for secure deletions — from the Standard 7-time pass, to 35-pass Secure Delete—a DoD-compliant Guttman secure delete algorithm.

In addition, you can have Paper Shredder graphically animate the shredding process to give you that added feeling of security. The application includes an emergency “Stop!” button in case you change your mind mid-shred.

As of this review, there is no trial download of Paper Shredder. It must be purchased from the Mac App Store for $6.99.

Supercan

Another third-party solution for securely deleting files is the free/donationware application called Supercan (note – at the time of this writing, the website for Supercan failed to download. You can also download the software on MacUpdate.) It includes the same security passes as Paper Shredder, but it allows you to selectively choose files already in your Mac’s trash can.

Supercan also shows you which hard drives your trashed files came from. And it too provides a graphic animation of the shredding process. However, for secure delete you need to select the “secured” button for each critical file you want securely deleted.

When you select the “Shred all…” button, you also get the option for selecting “Secured mode,” which will speed up the process of selecting and deleting files already in your trash can.

Securely deleting files may not be a need for most general Mac users, but if you happen to share your Mac with other people, or are planning to sell it one day, getting in the practice of securely deleting sensitive files is something you should do.

Let us know what you think about the secure deletion process on your Mac. Do you use it often, and have you run into any problems?