Security Corner

Nov 21 2008   2:02AM GMT

How to Quickly & Securely Erase a Hard Drive

Ken Harthun Ken Harthun Profile: Ken Harthun

Over at Ask the Geek, I often receive questions about how to properly erase a PC hard drive so personal data can’t be recovered. Clients also ask similar questions, particularly those involved in medical, dental, or financial practices. I’ve posted on this subject before, of course. “Paranoid About Hard Drive Security? Try This” outlined a two-step approach that works well, but is probably overkill for most, including those under regulatory scrutiny. The Center for Magnetic Recording Research (CMRR) points out that completely secure erasure doesn’t exist: erasure security is relative and is “a tradeoff between the erasure security level and  the erasure time required. A high security protocol requiring custom software or days to accomplish will be avoided by most users, making it  little used and  therefore of limited practical value.” Enter Secure Erase (SE).

According to CMRR, “The Secure Erase (SE) command was added to the open ANSI standards that control disk drives, at the request of CMRR… The SE command is implemented in all ATA interface drives manufactured after 2001 (drives with capacities greater than 15 GB)….

“Secure erase does a single on-track erasure of the data on the disk drive. The U.S. National Security Agency published an Information Assurance Approval of single pass overwrite, after technical testing at CMRR showed that multiple on-track overwrite passes gave no additional erasure.”

Secure Erase is a DOS-based program, so you need to make a bootable floppy, CD, or flash drive that boots DOS, FreeDOS, or a Windows 95/98/ME rescue disk. Download the freeware HDDerase, extract HDDerase.exe to your bootable media, boot the computer to a command prompt, and execute HDDerase.exe (HDDerase.exe must be run from an actual DOS environment and not a Window based DOS command shell).

In about an hour or two, depending on the size of the hard disk, you’ll have a drive that can be safely disposed of or re-deployed without fear. If you plan to re-deploy the disk, you’ll have to create a new partition and format the disk before you’ll be able to use it again.

I’ve used this handy utility many times to sanitize disks that contained data subject to the Health Insurance Portability and Accountability Act (HIPAA). All normal attempts to discover any trace of identifiable data on my test drives failed to reveal anything usable.

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