Hack 106: Truly Delete Data from Your Hard Drive
Platform Windows, Mac OS X
You’re about to sell, donate, or give away your old computer. Did you know that file-undelete software can easily resurrect those files you just emptied out of the Recycle Bin? Even though it looks as though you erased the files, in reality your computer has only marked the space they took up on disk as available — the 1s and 0s that make up those deleted files still exist.
The only sure way to securely and permanently delete sensitive files — such as a customer database, secret company documents, or personal photos you don’t want the guy who buys your hard drive on eBay to see — is to overwrite them several times with new data. Utilities to do this are available for both Mac and Windows systems.
warning According to a 2011 study by engineers at the University of California, current secure delete methods aren’t always reliable on newer, faster solid-state drives (SSDs), so you may want to think twice about selling a used SSD for now.1
Free, open-source Windows software Eraser (http://eraser.heidi.ie) permanently deletes files from disk using your choice of methods, including a Department of Defense standard (DoD 5220.22-M). Eraser can do both on-demand and scheduled scrub-downs of unused disk space on your entire hard drive; either way, it permanently deletes files.
If you’re passing a computer on to a co-worker or family member or selling it, delete your data as usual, and ...