In this video, we'll talk about secure data removal.
So when you delete a file, the problem is that it's not really gone.
And that is because the directory entry, which is the file name, is removed, but the blocks
that were used by the file stay in an unmodified way on disk.
And that means with the appropriate tools, you could get it back.
So when you delete a partition, what you really delete is the start and the end marker of
the partition.
And the data in the partition is not removed.
Same story.
You could get it back.
If you want to remove data securely, you have a couple of extra options.
First option is to use the DD utility.
DD, I-F-S-W, U-Random, that reads the U-Random device.
And the U-Random device generates random characters.
Apply that to an output, for instance, to output DevSEC1, which will irrevocably override
all blocks on DevSEC1 with random data.
Then you can be sure that nobody will ever get it back.
This is a little bit slower, but also more secure.
You could also use DD, I-F-S-Dev0, and O-F-S-DevSEC1, which overrides all blocks with zeros.
It's still very hard, but if you override with zeros, with high-end utilities, it could
be possible in certain circumstances to get the data back.
If you really want to be secure, better override your block device or your files with random
data.
There is a Thread utility as well, which can be used to delete files securely.
And the Thread utility is automating the work of DD, I-F-S-Dev0, U-Random, because it will
override the data blocks multiple times with random data.