Monday, June 3, 2013

Cyber Monday: Wipe free space, a hidden function

Data security is becoming more and more important, may it be to prevent identity theft or other fraudulent activities. The first step in making you laptop or desk top more secure is to make sure that when you delete something, it actually stays deleted.

FACT: In windows when you delete a file, you only delete its header but all of the data remains intact until something else overwrites it. An analogy to this is having a cover of a book ripped off, but keeping the book on the shelf until you have a new book to replace it. You can still open it up and read inside if you want. It's the same with data, you can easily recover that file and so can thieves. Therefore, the first step is to erase (or wipe) any free space.

Recently, I needed to wipe a USB drive clean and in doing so I found that there is a built-in function in Windows 7.  The great thing is that this tool is available all the way back to Windows XP Pro and it is also available in Windows 8!

So here is how it's done:

1. Open up a command prompt by typing: cmd.exe at the run menu

2. Then in the command prompt type in command as shown:

cipher /w:X  where X is drive letter for wiping the free space of a whole drive (will take more time than below, but more secure)

cipher /w:X:\somefolder  where X is the drive letter and somefolder is a folder. This will wipe a portion of the volume instead of the whole volume (not recommended, will take less time, but less secure)

This command with erase the free space 3 times. In the first round, it will overwrite the free space with all 0's, in the second round it will overwrite it with all 1's, and lastly with random numbers in the third round.

There are, of course, more vigorous ways of wiping data, but this does meet at least basic standards of unclassified data from the military. However, to be truly erased, one should look into what is actually approved by NIST (National Institute for Standards & Technology), Computer Security Center. They have a very small list of what is approved outside of physically destroying the hard drive and/or gaussing them. One such option is called Secure Erase which was made by U.C. San Diego, found here.

I hope this helps secure your data a little more.

You can find the source of the syntax's shown above here:

No comments:

Post a Comment

Your name and email will never be sold, distributed, or revealed to the public by any means.