Secure Data Deletion

How do I delete a file securely?

Windows:

  • PGP Desktop: "Shred" function
  • Heidi Eraser: Can delete already-deleted files securely

Mac OS X:

  • Finder: Secure Empty Trash (built-in)
  • Disk Utility: Can delete already-deleted files securely (built-in)
  • PGP Desktop: "Shred" function

UNIX: Wipe

How do I wipe an entire device securely?

For ATA, SCSI, USB, and Zip disks, overwrite using one of the methods below. A one-pass overwrite with random data is sufficient; degaussing is not necessary and will render a drive unusable. If the device will be disposed of (as opposed to being recycled) degaussing is a faster option.

Windows: Secure Erase

Mac OS X: Disk Utility (built-in)

UNIX: Wipe

CDs, DVDs: Destroy by incinerating, melting, or shredding to pieces no larger than 25mm2.

Tapes: Degauss/Contact the University Records Center for assistance with secure tape disposal.

Cell phones, PDAs, Printers: Delete data, then do a hard/factory reset.

Is there a faster way to securely delete a drive?

If you have an ATA drive, it may have a "fast secure erase" feature that will allow you to start the secure erase, protect it with a password, and prevent any drive access until the erase is complete. Degaussing is an option but will render the drive unusable.

How many overwrites are required to make the data unrecoverable?

A one-pass overwrite with random data is sufficient. Based on a report from NIST (National Institute of Standards and Technology) and research by the UCSD Center for Magnetic Recording Research, multiple overwrites take significantly more time and doesn't clear the remaining electromagnetic signal significantly better than a single overwrite. For more information, see NIST Special Publication 800-88 and the Center for Magnetic Recording Research.

What about shredding a hard drive?

To securely destroy/shred a hard drive, you can ask University Archives to pick it up and have it destroyed securely, which costs $0.52/pound. If you call University Archives, they'll walk you through the process of opening an account (if you don't already have one) and filling out a form before they pick up the drive(s) and have it destroyed.

ISC's Provider Desk also provides a degausser and "disk crusher" to members of Penn's technical community free of charge. Work with your LSP to find out which option is right for you. For more info visit Secure Drive Disposal.

Are there other options?

Visit the Green IT: Computers & Peripherals page for more information.