Permanently deleting files is something that a lot of people aren't aware of. Actually, most people think that once a file is deleted, it is gone forever. This is not the case. Hard drives write to the disk via magnetic charges, positive and negative correlate to 1s and 0s for binary. This is then interpreted into information for the computer to use and access.

When you delete a file, all that happens is a little modification to the binary that tells the computer it can be written over. So that means when you delete a file, it actually is still there until it is written over. So the simple solution would be to write over it, yes? No, actually. Files can still be recovered by taking bits and pieces of files and "guessing" what comes next, effectively recovering the file. You can write over a file up to 7 times, from my personal experience, before it becomes unrecoverable.

So, today in this Null Byte, we are going to be shredding some files to make them unrecoverable. This is a useful technique for when you have private information containing your social security number, or maybe just some private text. Be sure to do this before selling your computer as well, as I know people who buy used computers just to steal and recover credentials and other sensitive files.

We will be using the free software CCleaner to shred our files in Windows. Linux and Mac users should use BleachBit and Onyx respectively. I won't be teaching Mac and Linux because it is literally the same to use both programs.

Step 1 Download & Install CCleaner

Install CCleaner from their official page. Run the installer. Next > Next > Next > Finish.

Step 2 Run CCleaner to Shred Files

In CCleaner, you can specify how many times the program will write over your files or free space. For this I recommend using 10 passes. Anything beyond that is not recoverable for sure. Let's jump right into a video for a quick walkthrough of using this software.

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This will protect your computer from ever having sensitive data like passwords and cookies recovered. It will also speed your computer up! I suggest people start using SSDs more frequently, as this issue doesn't exist with a solid state drive because it's flash memory. SSDs only require one pass before data isn't recoverable.

That's it for this Null Byte. Come join the IRC to talk with me and the rest of Null Byte.