Destroying Data

Sounds simple, but not all methods remove or erase the data.

• Delete key does not equal erase
• Format command does not equal erase

Computer systems store data on a variety of storage media (e.g., hard drives, floppy disks, CD-ROMs, tapes, memory). It is important that data be securely removed from the media once the data and/or device is no longer required in order to prevent unauthorized disclosure of sensitive data.

There are a number of methods to delete data from a computer's hard drive (e.g., highlighting a file and pressing the Delete key, or emptying a recycle bin or trash folder, using system utilities to reformat the disk). These methods do not remove the data, they simply remove the pointers to the file. The data remains on the disk. Readily available software tools can be used to restore the data. Some are even free.

There are disk wiping utilities and programs available that will greatly improve the chances that your data cannot be recovered. Some programs erase the entire disk, while others allow you to select which files or folders to erase/shred. It is important that the utility or program provide an option to erase free space (temporary files).

Consult with your local technical support staff.

Below are options for various operating systems/media: Macintosh, Unix, Windows, and media.

Windows

* For R-Wipe & Clean, all users should select Tools and Customize and uncheck "event logs" and "firewall logs" under the System heading so that these important logs are always left alone.  Also, some users may want to uncheck "recent documents" or they can uncheck each time they use the program.

Macintosh

Unix

Other methods of destroying data include degaussing and destruction. Degaussing is a process by which the storage media is subjected to a powerful magnetic field to remove the data on the media. Degaussing may make the media inoperable; therefore use this method if the media does not need to be reused.

Destroying Media

Destruction is recommended for media (CD-ROMS, diskettes, tapes) containing highly sensitive data that cannot be wiped using the utilities and products described above. This is done by shredding disk platters, grinding the surfaces off of CD's, incinerating tapes, or cracking/cutting the media.  See Shred Right.

Note: The University of Minnesota has no business relationship and makes no endorsement of any product or service listed.

More information:

• Secure Data Deletion Standard U of M
• Secure Data Erasure (PDF) U of M Presentation
• Securely Deleting Files (PDF) SANS
• Securely Deleting Files on Multifunction Print Devices (PDF) SANS
• Windows Wiping-Secure Deletion Software Analysis (PDF) U of M Presentation
• UNIX Secure File Deletions (PDF) SANS