I was wondering about all those tools on the internet which are made to completely erase files from the harddisk.
Those programs could do 1 pass, or also more passes (like 35).
Why is this needed? When a bit on the disk is set to zero, why do it again on a new pass?
Also was I wondering why simple Linux commands aren't good enough to erase data, like:
dd if=/dev/zero of=/dev/sda bs=1M
This also completely erase all data, by setting each bit to zero. right?
So I should like to hear your opinion, counterargument or response on this.