Privacy and Information Security | University of Illinois

Disk Scrubbing FAQ

Q. What do you mean by "scrub" or "overwrite"?

A. Scrubbing a disk means writing over each bit on the drive with new (and usually random) information. Since sophisticated techniques exist for recovering data even from drives that have been "erased" or reformatted, the Department of Defense has recommended that drives be overwritten seven times before being recycled; drives containing top secret information are never recycled but physically destroyed.

Q. When can I just throw away a drive?

A. You should never simply toss a drive into the trash. If you feel a drive is not worth repairing or the time it would require to scrub, contact surplus. Inform them that you want to dispose of a drive and they will come out and inspect the drive. Once they approve the scrapping of a drive or other media, they will arrange for its secure disposal.

Q. The drive in the PC I want to send to surplus is broken. Does this mean I have to fix it and scrub it before I dispose of it?

A. No. To ensure the broken drive is handled properly, contact Surplus to have them arrange for secure disposal of the drive.

Q. How do I scrub or wipe a disk multiple times?

A. While you are free to use the disk scrubbing utility of your choice, the following software (available only to campus technical staff) is recommended:

* Windows: DBAN.
* Linux: DBAN
* Mac: Apple Disk Utility Secure Erase.
* Unix and Unix-like Operating systems: If your hardware is Intel based and capable of supporting Linux then use DBAN. Otherwise boot to a CD and run dd if=/dev/zero of=/dev/hda multiple times over the disk.

Note 1: The precise format of the dd command will vary depending on the flavor of Unix you are using. There are a few freeware disk scrubbing programs for Unix available such as Autoclave and Wipe. You may wish to explore these as an alternative.

Note 2: Most commercial packages will overwrite a disk a maximum of 7 times by default.

Q. So what exactly do I need to do before sending a machine to surplus?

A.  See the OBFS page on how to Dispose of Unneeded Equipment.

Q. Where do I get the disk scrub labels?

You can make your own labels to place on the surplus/scrapped machine by downloading the following file and printing it onto Avery label paper.

Avery 5160 (30 labels/sheet, 1" x 2 5/8")

Avery 5163 (10 labels/sheet, 2" x 4")

Other Questions or Comments

Please feel free to contact us at securitysupport@illinois.edu with additional questions or suggestions.