Last week I mentioned an additional menu item I find on my computers when I right click on my Recycle Bin in Windows.  The one I told you about last time was Icon Restore and this week the menu item is “Erase Recycle Bin”.  The program that provides this feature is called “Eraser” (http://bbs.heidi.ie/eraser/).  When you right click on your recycle bin or any folder or file you can choose to eraser them so that they can not be recovered later.

I have talked before about how your computer deletes a file by changing the file’s name, which in turn makes the file undetectable to you. It also tells the computer that the space the file occupies on the hard drive may be used to “write” other data on top of whenever the space is needed.

If a file is deleted and no other information has been written over the old file, it is still there and could be retrieved using one of the many file recovery programs out there.  If another file is stored on that “empty” space over and over again the file will most likely be unrecoverable sometime in the future.

To delete the file permanently you need a program like Eraser. What permanent deletion programs do is to write over the deleted file once too many times.  Again once, an overwritten file will be made unusable and more importantly for security purposes, unrecoverable. There are many of these types of programs on the market.  I have used “Eraser” for several years and it seems to work very well so I recommend it; however, as with all software downloads proceed at your own risk.

“Eraser” will allow you to choose how many times you want the files over-written, either 1, 3, 7 or 35 times. The U. S. Department of Defense suggests three to seven overwrites to render a file unusable. Peter Gutman, magnetic storage specialist at the University of Auckland reports that, “…it is effectively impossible to sanitize storage locations by simply overwriting them, no matter how many overwrite passes are made or what data patterns are written.”

Having read that you should know that the 35 times overwrite is called the Gutman recommendation for secure file deletion.

Also note that it can take quite a while to overwrite large files 35 times so plan ahead.  The many spy movies that you may have seen show computers’ hard drives being deleted in a few seconds are not true. So if you choose to delete your entire hard drive you may need to plan anywhere from a few hours to a couple of days to perform a total erasure.

Keep in mind that that is sometimes possible to recover a file by very high end programs no many how times it is overwritten.  So if you are a spy hiding things from an evil government watch out, they may still be able to retrieve your secret files.

This entry was posted on Tuesday, June 24th, 2008 at 6:31 am and is filed under Columns. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.