Your disk is like a file cabinet, there’s also an index folder where for example it says that “your file.txt” is in cabinet C7. You go there and there’s a sheet of paper written in pencil with the contents of your file. In this analogy here’s how several solutions work:
Delete the file: throw away the index folder. Now if you need to write to disk you might think C7 is free and when you go there to write something else you find the old paper, which you erase and write on top. But if someone gets to your cabinet before that and they open C7 your file Will be there in its entirety, there just isn’t an index telling you which cabinet to open.
Zero wipe: you go to C7, erase the file, and then throw away the index. Now if someone gets to your cabinet they might go to C7 but all they see is a white sheet of paper. However it’s technically possible with a white sheet of paper to see what was written before, so this is considered better but not perfect.
Random wipe: same as before, except you erase and write random stuff on the sheet of paper. So it becomes a lot more difficult to recover what was there.
Multiple passes: Same as before, but you do this several times, so after dozens of random writes your original data should be completely impossible to recover.
Your disk is like a file cabinet, there’s also an index folder where for example it says that “your file.txt” is in cabinet C7. You go there and there’s a sheet of paper written in pencil with the contents of your file. In this analogy here’s how several solutions work: