Data Destruction

What Happens When You Delete a File

Because of the way these allocation tables work and the way we store data, we really don't delete the data when we delete a file, and that can become problematic. So we really need to make sure we take extra steps in deleting the data on our drives before we hand over our computers to somebody else, or before we turn it into the junkyard, or whatever we're going to do to dispose of our computers.

What happens when you delete a file is it just deletes it from the allocation table. So here we have file.txt, and if I were to remove it, it would be removed from here, and then the clusters that that exists in would just be marked as being available — that is, now something can be written over. Let's say we save some changes to file two; then maybe this one gets written over. But this data still exists until it gets written over.

What that means is that anybody that has access to your computer can download a special program and then scan for this data and be able to collect that data. So you can't just turn your computer over to like a thrift store, or throw it away, or somewhere where somebody has access to the drive, because now what they can do is they can scan that drive and retrieve all the information on that drive.

This is true even if you're deleting partitions or volumes. All it's doing is it's deleting the references and the structure, and even if you go and reapply some sort of volume or partition in there, the data can still exist in there until it's written over, which could be a long time.

Physical Destruction and Data Wipes

To make sure that our data is not going to get into the wrong hands, we have to perform some sort of data destruction. We can either physically damage the device — like we take a hammer to it, take a drill to it, take something where we actually destroy the capabilities of that ever getting read again. And we have to really make sure that it's destroyed properly and that there's no chance of actually getting that data back.

Or we do something called a data wipe, where we wipe out the data on there so that the media could still be used again. There are a lot of different ways to do a data wipe. For instance, if it's magnetic media, we could use strong powerful magnets that we can go and run across there to make all of the polarities change. Another way we could do it is with software. There is software out there that will rewrite over these clusters, so it'll write ones and zeros across here. And for it to be official, like for top secret documents, it actually has to take many different passes across here, so it'll start wiping this data by writing all these ones and zeros.