Number 275 - April 2006

Erasing Hard Drives
Compiled by: Napa Valley Personal Computer Users Group
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: www.killdisk.com/eraser.htm    Autoclave v0.3 http://staff.washington.edu/jdlarios/autoclave/    Paragon Disk Wiper v5.5: www.disk-wiper.com/    Eraser: www.heidi.ie/eraser/    DBAN: http://dban.sourceforge.net/ TOGGLE Editor's Note:    Don't forget, one of our favorites, BCWipe which you might find available for free.
Number 275 - April 2006