Erasing
Hard Drives
A guide to
surplusing computers and electronic storage devices.
One of the greatest concerns people have when disposing of
their old computer equipment is the removal of the very personal data contained
on them. The dangers of not properly erasing the hard drives is in the
possibility of unwanted exposure of sensitive personal or business data and
unwelcome publicity.
The DOS and
Windows command to delete files do not delete the data from your harddisk. They
merely delete their own record of the fact that the area of the disk they
occupy is unavailable to other uses. To do this, the command merely unlinks the
file in its File Allocation Table (FAT) by changing the first character of its
name to a special byte. Consequently, the undelete commands merely have to
change the character back to restore the data, as is amply demonstrated
retrieving deleted files from the Windows recycle bin. Contrary to popular
belief, reformatting the hard drive does not affect the disk data. The command
merely formats a new file record for that logical drive. It does not remove the
data until the system overwrites it with new data.
To ensure
confidentiality and in some cases to ensure compliance with software license
agreements, binary overwrite programs that “zero out” the data have been
developed that overwrite all addressable storage and indexing locations on the
drive. Many programs meet the Department of Defense security standard 5220.22-M
by utilizing a three pass binary overwrite of the drive with zeros (0x00, 0xFF)
and random data. This is the only way to be sure that the data has been
destroyed and cannot be recovered even with the use of special computer
forensic and file recovery tools.
Many such
programs are available “freeware”, “shareware” and fee based from the
internet. Most programs are executable
from a bootable 1.44Mb floppy disk the user creates following specifically
detailed instructions. The process is relatively easy and can be accomplished
with a very small investment of time. The following are URL’s that may assist
in the process;
Active @
Kill Disk: http://www.killdisk.com/eraser.htm
Autoclave
v0.3 http://staff.washington.edu/jdlarios/autoclave/
Paragon
Disk Wiper v5.5: http://www.disk-wiper.com/
Eraser: http://www.heidi.ie/eraser/
DBAN: http://dban.sourceforge.net/
Compiled
by: Napa Valley Personal Computer Users
Group
e-mail: recycler@nvpcug.org