Most secure way to delete data

[realWasabi]

Hi!

I hope it's alright I ask this on this board - I couldn't find a "deletion of data"-board.

I'm about to sell some used hard drives (1x1TB and 2x2TB). The drives have had alot of personal stuff on them as well as business data, so I need to be sure they are wiped to a point where the data can't be recovered.

I tried google which gives me alot of options, but the various sites tells alot of different stories.

The most popular wipe methods seems to be:

1. DBAN (Dariks Boot and Nuke)

2. In a linux command prompt: dd if=/dev/zero of=/dev/sda bs=512

3. In a linux command prompt: dd if=/dev/random of=/dev/sda bs=512 (apparently this should be more secure as linux then writes random numbers onto the disk instead of just zeros.)

What are your thoughts? What would be the hardest to recover? Would it make a difference to make several passes?

[BlackST]

Either internal security erase (MHDD can do it) or simple zerofill of the drive is sufficient for the vast majority of security requirements. Otherwise use something that is DoD compliant for your peace of mind (several passes with different patterns). This argument was discussed many times. Expect several hours for this kind of things to end.

The best solution would be factory procedures that involve recalibration and internal W2W reformat , but require dedicated equipment and know how and is even slower (I do it, if you are really interested). You get a "like brand new drive in return.