When you hit the delete button on a file, is it really gone?
Most of us know the answer, at least initially, is no. We know we can resurrect files that a clumsy keystroke, an inquisitive toddler, or some other source of mayhem has inadvertently removed from our documents folder. A quick trip to the virtual recycle bin, a search and a click, and it’s back where it should be.
But what about files that are deleted from the recycle bin? And how about files that are supposedly unrecoverable, as when a hard drive is reformatted? Are those gone for good, or are they recoverable?
The answer lies in how your computer stores its information.
How Does Your Computer Store Stuff?
Cast your mind back to elementary school, or whenever you last wrote in pencil and did a lot of erasing. Remember how, if you wrote dark enough, you could still read what you wrote, even after you erased it? And sometimes a shadow was still visible, even after you wrote over it? Well, that’s kind of how data is on your computer.
As your computer stores data, it ‘writes’ it in a specific area known as a block. For our purposes, this block is our piece of paper, and the file — no matter what kind it is, picture or video or text — is written in pencil.
When you delete a file, it’s like you’ve erased it, but the words are still legible. Your computer can bring it back in most cases. The only time this changes is when more data is written over the exact block (or blocks) where the information for your file was contained.
When Files Are Really Truly Gone
Conventional wisdom says that when your hard drive is wiped clean by reformatting, all data on it is gone. Unfortunately, this isn’t altogether true. For one thing, each operating system formats drives according to its own rules. Secondly, there are two kinds of formatting: full and quick. A quick format basically just deletes partition information. This doesn’t destroy the data written on the blocks per se; it just removes information about how to find them. The data is still in the block (and recoverable) until the computer writes over it with other data.
Even when you think data is truly gone on a reformatted drive, there are programs available to recover it. You can get them quite easily online. While this is handy for the times you accidentally reformat a drive (hey, it does happen), it’s less positive when you’ve sold or lost your PC and someone else uses the program to get your erased information.
So, how can you really, truly delete files?
- Run a full format. This takes longer than a quick format, but it rewrites the individual blocks with strings of nonsense, making data much harder to recover.
- Do it again. And again. In fact, security experts consider a cycle of five complete formattings to be the minimum safety standard.
- Or just get a file shredding program. If you’ve only got a couple of sensitive files to erase, a file shredding program overwrites the info in a similar manner to a full format.
Keep tuning in to the TechSperts blog, and we’ll keep coming up with interesting IT stuff for you to read about!
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