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[True story/Explanation] What happens when you delete files from your PC/Hard drive

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avatar Dr_Steve
Level 36 : Artisan Robot
35
Tl;dr
* When you delete files, it isn't actually deleted

* In reality, it is just marked inaccessible by the file system

* You actually need to delete the files bit-by-bit to actually destroy
your files without destroying your hard disk. Yet some authorities are
actually still able to recover data, even from damaged disks

Many times, you expect to delete files to prevent people from reading your confidential files (for example), or you don't need them anymore, you delete them, and you assume "No one can find them!" , but, in reality, when you delete a file/format a storage medium (like an HDD (hard drive), for example), it isn't actually deleted! 

Instead, it is just marked in-accessible by the file system (which kind of means nothing). That means, that, anyone with the right tools, can recover your confidential files!  What exactly it does is deletes is something in the MFT (Master File Table) which is essentially the map of the files. So essentially, it just removes itself from the map, but not the file itself.


If you want to actually destroy your files (instead of/without destroying your hard drive), you would want to overwrite their contents!  The same thing can happen if the partition tables are damaged, that has the same scenario as mentioned in this blog (you can still recover it with the right tools). Additionally, some programs exist out there to securely erase files, and in addition the OEM of your PC, or the vendor of your HDD may have some software tools on the hard drive, too! Even better, as I mentioned about the MFT, essentially a map for your files, you can even defragment your hard drive, to help remove traces, as blocks consumed by that  file in question can be overwritten as they're marked as empty

Even with very complex tactics, and even when you physically destroy the disk, sometimes authorities are still even able to recover data from an HDD, and worse, for SSD's you cannot just use a tool to overwrite the contents because you cannot overwrite NAND flash memory (OK I think you can, but to, in my opinion, small extents only [which is why you must NOT defrag your SSD])



This is also a true story, when I had the question to this blog, when I had a PC a few years ago, and my grandparent said about what happens when you delete a file, and they thought that  "It went up to 'Cyber-space' ". That is kind of true, however.
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Wow I actually always wondered where your deleted files go.
Thanks for the explanation :)
  • Dr_Steve
  • Level 36
  • Artisan Robot
  • August 7, 2015, 5:02 pm
You're welcome! The same happens if the partition tables are deleted/overwritten (usually done by a virus btw).

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