How to securely erase your hard drive or SSD

The siren has sung and you’ve finally succumbed to her call: You’re the proud owner of a shiny new PC, a faster SSD, or a bigger hard drive. It’s time to sell or donate your old gear and start playing with your new toys, right? Not so fast. First you need to securely erase the data off your old hard drives so you don’t become a victim of identify theft.

Simply deleting the data off your hard drive doesn’t erase it as you might expect. Instead, NTFS (the file system used by Windows PCs) just hides the data from immediate view, leaving it to be overwritten when a new file takes up residence on the drive. That’s a workable scenario for everyday use, but it could spell disaster when it’s time to part with an old machine.

To truly destroy the data on your storage device you need to take more drastic (and time-consuming) measures to overwrite your drive space with ones and zeroes. That’s where this guide comes in.

Different technology and scenarios call for different tools. We’ll identify the best secure-erasing utility for every job, no matter what type of drive you’re using—even USB flash drives. If you want to erase only specific files, we’ll show you how to do that, too. Best of all, almost every solution discussed here is free.

Before you begin

William Warby (CC BY 2.0)

Back up your data! Once these programs get to work, you can’t go back for a forgotten file. This is a one-way street to data oblivion. Also if you’re erasing the drive on a laptop, be sure to plug the notebook in before you start. If the battery gets spent and the power goes out in the middle of a disk wipe it could spell disaster for the drive.

With that out of the way let’s talk terminology. Drive-wipe utilities let you specify how many “passes” the software makes. Each pass signifies a complete overwrite of the data. A utility that makes three passes overwrites your drive with ones and zeroes three separate times. The more times you overwrite your data, the less likely it is to be recovered. Some utilities support “Gutmann”-level protection with 35 passes, but three passes is enough for the U.S. Department of Defense’s “Short” specification and for numerous militaries around the globe.

If you do choose to erase your data with any of these methods, you do so at your own risk—which is why we advise making a backup before you begin. Nevertheless, we have used all of these methods successfully in the past.

Securely erase specific files with Eraser

If you need to delete only specific files and folders rather than entire drives, the open-source Eraser is the tool for you. Just boot up the program, click the arrow next to the ‘Erase Schedule’ option at the top of the screen, and select New task. From there, a window pops up with the task and time-scheduling options. Click Add Data to select the files to wipe and choose an erasure method. (I usually go with the DoD three-pass option.)