Would you put a file cabinet in that weekend yard sale or charitable organization's truck with financial records, personal documents, and photo albums still inside?
How about leaving the office trash can overflowing with sensitive documents?
Similar breaches of personal security can occur when bidding farewell to a computer unless you properly delete folders and files.
Readers' messages about permanently removing files peak with the return of warm weather, when old computers go into yard sales. More trickle in around the year from individuals who change jobs and worry that the boss may be able to recover deleted files.
The messages make one thing clear:
Many people don't realize that moving a file to the Windows Recycle Bin, or deleting it with a program, doesn't really eliminate the file.
Files put in the Recycle Bin stay there until someone empties the bin. To empty the bin, right click on the bin icon, which looks like a trash can, and select Empty Recycle Bin. Until then, files can be recovered with a few mouse clicks. Left click on the bin icon, highlight files you want to recover, right click in the highlighted area, and select Restore.
Even after emptying the bin, “deleted” files remain because a computer's master control program doesn't shred the file. Rather, it removes the file name from the hard disc index, so that the file seems to disappear. It also marks the file's disk space, “Now Available For Use,” so that a new file can overwrite the space.
The original file, however, remains on the disc. It may stay there for weeks or months, until the computer overwrites the file region with new data. Even then, data in the original file may be recoverable.
When a computer writes data to the hard disk, it changes the orientation of “magnetic domains” in ways that store the information in a file. Writing new data to that area may leave many of the domains in their original orientation.
Special programs can recover at least part of the “deleted” and “overwritten” file.
That's why government intelligence agencies take great care in deleting files. The National Security Agency, for instance, reportedly overwrites each data area seven times with a pattern of “0s” and then again with “1s.” The Department of Defense regards a file as deleted only after it is overwritten with patterns of 0s, 1s, and nonsense data.
Several good, inexpensive commercial “file shredder” or “file wiping” programs use similar approaches. They include Quick Wiper (www.aks-labs.com) and Eraser (www.tolvanen.com/eraser/). Some can be downloaded for a free trial.
Deluxe anti-virus packages, such as McAfee Internet Security (www.mcafee-at-home.com) and utility programs like Norton Utilities 2002 (www.symantec.com) include file shredders.
How much file deletion security do you need?
It depends on the sensitivity of your files. Many home computer users may feel comfortable with just deleting their personal files and emptying the Recycle Bin. Others may want to delete the contents of certain files, paste in fresh data, save, delete that, delete the file, and empty the bin.
Some may need the extra security of a file-shredder program.
Don't forget other basic security measures when parting with a computer.
Delete e-mail from the inbox, sent messages box, and deleted items box. Run Internet Explorer, click Tools on the toolbar, select Internet Options, and under the General tab delete cookies, delete temporary Internet files, and clear the history. From the Windows Start Button, select Find, select Files or Folders, and search for other temporary files by keyboarding (*.*tmp ) without the parenthesis. Delete them.
Michael Woods is The Blade's science editor. His column on computers and technology appears each Saturday.
First Published April 20, 2002, 11:01 a.m.
