Jul
29
2010

Think that file you “permanently deleted” from your computer is gone for good? Think again! Why “deleting” files is a huge misnomer.

When you have no use for a particular file any more and you either want to save hard drive space or stop prying eyes from seeing it, it is common behaviour to delete it from your computer. Like any good computer, Windows appears to make “deleting” a file very easy – just press Delete, or right-click and choose Delete, and it will put it in the Recycle Bin so you can decide whether or not you REALLY wanted it gone. Empty the Recycle Bin or press Delete again while it’s inside, and the file disappears from your computer.

You’ve probably thought that once you’ve deleted a file this way, it’s gone for good and you can forget about it, right? Wrong!

What do you mean “delete” doesn’t delete?

Have you ever wondered how a computer can find files so easily when Hard Drives are so large and the file could be placed anywhere on the round surface of the Drive’s disk? Like a shopping mall has a directory to help you find each store, your System keeps a “directory” of all the files on your computer and their physical location. This directory is called the “Master File Table” or “MFT”, and is always placed in a specific part of the drive so the System can find it. Whenever your computer needs a file, it just checks the MFT to know where to look for the file, and goes to every place it has to in order to read the file and start using it. And every time a file is created, changed or deleted, the MFT is updated to let the computer know about the changes.

The main flaw about computers though, is that they can only do two main things with files – read them; and write to them. These are the only things that a Hard Drive can physically do; everything else comes from the System running on top of it. So, when you “delete” a file, it isn’t gone from the Hard Drive, because the Hard Drive can’t remove it. Instead, the computer removes any information about the file from the MFT, basically leading the computer to “forget” it existed, and where it is. The location of the file is marked as free space, so anything can use the space the file took up whenever the need arises. But the file is still there, on the Hard Drive; and until something writes over it, it will stay there for as long as the drive still works.

What does this mean?

If you “delete” a file without properly erasing it, it could remain on your computer almost forever, until the time comes that the space it originally owned is needed for something else. This means that unless you use the computer really, REALLY often, anything in those files could still be there and could potentially be recovered. If those files contain sensitive data, such as personal information; banking details; passwords and so on, someone could steal that information without you even knowing it’s still there!

I’m scared! Is there anything I can do about it?

The only real way to really delete a file for good is to write over its space until nothing remains of the original file. But on computers with lots of storage space, this is very unlikely to happen because there’s so much other space the computer can use as well.

But there ARE things you can do about it! For some years now, there has been a slew of “Secure Erasing” software products out there for people to download or purchase. As well as making your computer “forget” about a file and mark it as free space, these programs actually FORCE your computer to continually overwrite the spot(s) on a Hard Drive containing a file until nothing remains, and then replace it with dummy data that has no meaning or is completely blank.

In the future I will try to find the best of these software and create articles telling what these products are, where to find them and how well they work. Until then, search around, ask questions and hopefully you’ll find something that works for you. And remember – always safety first.

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