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The Case of the Shredded Files

Posted By Randal On May 7, 2012 @ 1:51 PM In File & Disk Management,Security Help | 2 Comments

Joe from DE writes:

Other than for security purposes, does shredding files gain back hard drive space? How does it work, exactly?

Hi, Joe.  Thanks for the great question.

Whether you delete a file from your recycle bin or shred it, the space is made available for your computer to use.  Although in either case it is still technically taking up the same amount of space on your hard drive, your computer can still overwrite the information.  The big difference is that when you simply delete a file from your recycle bin, the file is still there and can be recovered using specialized forensic software.  When you “shred” a file, the computer overwrites the information with random data.  So, although the file is still there, and still taking up the same amount of space, the information contained in the file is gone and cannot be recovered anymore.  Think of it this way: when you write something on paper with pencil and then erase it, you can still see a faint version of the information on the paper.  Shredding is like using a pen to make random symbols over the information that you’ve written in pencil, so, although the information is still there, it’s covered by the random symbols, and as such, unintelligible. 

So the primary reason for “shredding” is security.  If you delete something and you don’t want anyone to ever be able to access it again, you shred it.  Most free shredding programs will make one “pass” over the program, writing ones and zeroes over the information.  Professional shredding programs, on the other hand, will make one pass writing ones and zeroes, and then further passes writing different nonsense over the previously written information.  If I remember correctly, the shredding process that the military uses makes eight passes over the file in question. 

I hope that this helps.

~Randal


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