how “permanently deleted” files in a computer are still accessible by data recovery tools?

Question

So i was enjoying some down time for myself the other night taking a nice warm bath and letting my mind wander when i suddenly recalled a time when i worked at a research station and some idiot managed to somehow delete over 3000 excel spreadsheets worth of recently collected data. I was charged with recovering the data and scanning through everything to make sure it was ok and nothing deleted…must have spent nearly 2 weeks scanning through endless pages…and it just barely dawned on me to wonder…exactly…how the hell do data recovery tools collect “lost data”???

I get like a general idea of like how as long as like that “save location” isnt written over with new data, then technically that data is still…there???? I…thats as much as i understand.

Thanks much appreciated!

And for those wondering, it wasnt me, it was my first week on the job as the only SRA for that station and the person charged with training me for the day…i literally watched him highlight all the data, right click, and click delete on the data and then ask “where’d it all go?!?”

In: Technology

Answer 1

Imagine that a computer’s hard drive (HDD/SSD) is a warehouse. To find things in the warehouse, you have and inventory list of numbers which point you to look for an item in the warehouse (For example, Aisle 5, Shelf 12, Bay 6).

When you delete a file, it is like removing the record from your warehouse’s inventory list. This indicates that the space in your warehouse can be used for other inventory even though you haven’t removed the old “junk” inventory yet. The old junk inventory remains until the space is needed (overwriting in a computer) or removed as part of a clean up operation (aka, emptying your recycle bin).

Data recovery tools are like sending someone to take inventory at your warehouse- they can find and re-record the items (files) that were deleted but haven’t been actually removed yet.

Imagine that a computer’s hard drive (HDD/SSD) is a warehouse. To find things in the warehouse, you have an inventory list of numbers that point you to look for an item in the warehouse (For example, Aisle 5, Shelf 12, Bay 6).
yet. The old junk inventory remains until the space is needed (overwriting in a computer) or removed as part of a clean-up operation (aka, emptying your recycle bin).