What is the fastest way to securely overwrite an old hard drive? [duplicate]

Solution 1:

I used CCleaner a few times, which is a free tool that does the job.

Solution 2:

You should use DBAN or similar tools.

Solution 3:

Just fill it with zero bytes, on Linux with something like

dd if=/dev/zero of=/dev/sdb bs=1M count=1000

this is enough for most purposes and is the fastest thing available.

(there is probably an equivalent on your system, and you could boot a live-boot CDROM linux to run it otherwise)

Of course, if you had military grade secrets on the disk, and/or you are afraid of the CIA, it is probably not enough. (In that case, destroy physically your disk).