Helping people with computers... one answer at a time.
Creating a large file and then deleting it overwrites anything on your computer's free space: but that's still not enough to protect yourself when giving away a computer.
There's much discussion on how to insure personal data cannot be recovered when a PC is sold or scrapped. We know that a standard file delete will not really delete the disk data, but just de-allocate the sectors making them available for use when other files are created or extended. Would a simple solution be to use a file shredder tool or simply to use a script to create a large junk file, which would fill all available space thereby overwriting the data from old deleted files?
In this excerpt from Answercast #37, I look at how to protect your data when you give away a computer.
In a sense, yes.
In many ways, that's pretty much what a file shredding tool does or what a secure delete tool does.
Well, that's essentially what creating a large file would do:
If you just filled that file with random data,
Filled your entire hard disk (in other words, used up all of the free space on the hard disk for this file),
And then deleted it.
You would have overwritten all of the free space on the disk.
Now, I am going to say that's not enough. It's not enough because there is more to your system than just what's in its free space. You're talking here about when a PC is sold or scrapped.
So what you really need to do is you need to delete everything; even the files that are there. You don't know:
What's stored in the registry.
What's stored in the swap files.
What's stored in other files that Windows maintains that you might not want to have other people able to get access to.
That's why I so strongly recommend that before you give a computer away or even just recycle or scrap a hard disk, that if you can (if the hard disk is still working), you run a utility like DBan on it:
That securely and completely erases everything on the hard disk whether it's in use or not.
The net result, after running DBan, is a completely empty hard disk. And
that's exactly what you want to give away. You don't want to give away any of
your data whether it was left over in free space or actually still in use by
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