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System Analysis, Design and Support

Really Deleted ? How to securely overwrite free space

When you delete a file from your Windows computer, instead of deleting the actual file, it simply marks the space the file is using as free to be over written. Until the file is actually overwritten it is easily recoverable by file recovery software. One way of making sure that your data is not easily recoverable is to simply overwrite all the free space with random data. In Windows, you can do this by starting an administrative command prompt and run the command:

cipher /w:D

Where D is the letter of the drive you want to overwrite the free space on.

It will overwrite the free space in three passes.

  • First with all zero’s
  • Second with all one’s
  • Then with random numbers

That’s all there is to it. It can take 30 minutes or more to overwrite your free space.

P.S. I say “not easily recoverable” as it is still possible to recover the data forensically. Just ask Hillary.