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

It really depends on what you mean by “deleted”, but you seem to have an inkling of that.

In general ‘deleting’ data simply means a command that tells the computer to forget something important is contained in that portion of memory. Technically the information is still, literally physically, there the computer just doesn’t know it anymore. Kind of like a dictionary where the page numbers are deleted. A specialist, or special software just needs to know where to look and it can be restored.

“permanently deleted” implies something actively *destroyed* the old information. In this the computer might literally go and write over the old data with new garbage data. In this case the dictionary pages weren’t just deleted, the pages were bleached and then a copy of James Joyce’s “Finngans Wake” was written over it. In fact, the computer probably then bleaches the pages again and puts “Twilight” over Finnegans Wake, and then bleaches it again and writes a Trump speech over that. Literally random, incoherent gibberish over gibberish over gibberish. In this case whatever you deleted cannot be recovered and is truly erased from the drive. Period.