You have a good point with the bad blocks. But just writing to all the free space on the disk should cover the wear leveling issue.
I was mainly referring to the old wives' tale that data could be recovered unless it was overwritten 7 times. I've never heard of anyone recovering data that had been overwritten just once.
I do understand, however, that there is no visual indication that the data has been erased, and that can be disconcerting. In that case, a ball peen hammer liberally applied should satisfy anyone.
> You have a good point with the bad blocks. But just writing to all the free space on the disk should cover the wear leveling issue.
I don't think you have a good mental model of how a SSD works. let me try and help.
Say you buy a SSD with 100 GB of space. It is really a 110 GB or 120 GB drive. You can only use 100 GB of it. During use, the drive will often "see" a bad sector, and remap it on the fly to one of the spare sectors it has on the device. When doing this - it does not wipe or do anything fancy to that "Bad" sector. So over time, small chunks of data get left behind in "Bad" sectors. You can format every single byte of visible space, but that will not touch "bad" sectors. Your format would only hit the 100 GB of space, it would totally ignore the 10 or 20 GB of spare or bad capacity.
So if someone gets your freshly wiped SSD, they can dig up all of the bad sectors and see what is there. Maybe nothing, maybe a part of a file that has your production credentials. The police and NSA have tools to do this fairly automatically. I suspect organized crime would as well.
Just writing some 0s to a SSD is NOT a safe way to wipe it.
This is the spec where people come up with. The idea is that you write a 0 pass, a 1 pass, and then a binary switch (3-pass). People have taken it to extremes with 5 pass and 7 pass BS. Honestly, doing 0's over the drive once is probably sufficient as long as you get every single byte.
I read about that 7x stuff back in the 80's. As I recall, it was based on the idea that you could look at the disk with an electron microscope or something and it could pick up echos of the previous data.
If this actually worked, data recovery companies would make a mint recovering overwritten files. But I've never heard of anyone advertising such or ever accomplishing it.
> data recovery companies would make a mint recovering overwritten files
Data companies make mint recovering deleted files and hard drives that have been disabled by the motor or control board just failing but recovering a full file from a hard drive with a microscope would be ridiculous.
