How should I dispose of my hard disk securely?

Q) I wish to dispose of an old computer and I understand that the best way of protecting the personal information on the hard disk (my bank details and so on) is to remove the hard disk and break it up with a hammer, and then the other computer parts can be used by a third party. Can you advise how to go about this process?

A) The rather odd advice to smash your hard disk if you’re getting rid of a computer was recently propagated by a national magazine (not one related to Computeractive, we hasten to add).

While it’s certainly one way of making sure the data on your disk can’t be accessed, it’s not the most practical. For one thing, it’s dangerous – there’s a risk of being hit in the eye by a small part flying off the disk’s casing – and second it is considerably more trouble than it’s worth.

Let’s go back to basics: the reason you need to make data unrecoverable is that, because of the way hard disks work, deleting something doesn’t really mean it’s gone. When you delete a file in Windows it remains on the disk but the computer ‘forgets’ about it. It’s still easily recoverable. Even formatting the hard disk, which wipes it clean, leaves traces of your old data which, again, is still recoverable with dedicated software.

There is software available, though, that will not only wipe your hard disk clean but will overwrite it with random patterns of data so that the old data (your confidential files) is truly hard to recover.

There’s some argument over how thorough the software needs to be, but one of the most popular free tools, Eraser, allows you to set a number of ‘passes’ – that is, the number of times it overwrites all the data on the disk.

How many you use is up to you, but obviously the more passes, the longer it will take. One or two is probably enough for most people, since criminals are more likely to move onto an easier target than waste time recovering masked data.

Either way, using Eraser or other software (most all-in-one utility programs, disk tools software, system tweaking or tune-up software and some security programs will offer the same features) is certainly easier than taking a hammer to your disk.

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12 Comments

Comment by TekBudda on July 16, 2009 at 9:38pm: I actually work on a team that does this for a living. Ins hort we decommission old machines & install the new ones. The decomm'ed machines are then either donated to a computers for schools charity or sent for recycling...depending on the shape they are in.

We try to wipe the hard drive in the machine first but if there are any errors or other problems we remove the hard drive & take it back to the shop. From there, we may try to wipe it again or just plain drill it out & the hard drives are recycled

The only variation on this is server drives. They are just plain drilled out and destroyed. Tapes & other data storgae devices like CD's, floppies, etc. are broken up...destroyed & recycled as well.

Comment by Glenn on July 12, 2009 at 8:58pm: Oh, something I forgot before I pushed the button:

In the realm of 'whimsical but not practical," my Inventiveness Award goes to Chip Black. Man, will that data ever be safe! :-D

Honorable mention goes to System001. Only problem is that you may have trouble finding a college science department that would be amenable to using their supply of sulphuric acid for such a use. I found high-grade Sulphuric acid for sale for around $25USD for 250 ml, and that probably wouldn't be enough to do the job (though I don't know...I've never tried it). Enough to do the job might start being expensive...at least expensive enough that you could buy a new hard drive. Then there is the waste disposal problems, and talk about personal safety and the possibility of injury...!

Inventive, though! :-)

Comment by Glenn on July 12, 2009 at 8:31pm: Of course, using software to wipe the disks carries with it a few caveats.

First is that, if you're truly paranoid about the information you have on that drive, even a major wiping is not sufficient to wipe all traces. It is expensive, but parts or all of that data can be recovered with an intensive (and expensive) enough forensic scanning.

Secondly, consider what is involved in running wiping program. When you run a hard drive wiping program, random 1s and 0s are written to every location on the disk in order to over-write any information that is recorded on it. One pass is a lot of hard drive operation, and a lot of write cycles. Multiply that by the number of passes you indicate (I've read that DOD standard is 7 or 8 passes, and then you could use the Gutmann standard, which is 27 passes) and it becomes a WHOLE LOT of operation and write-cycles. This, of course, will SUBSTANTIALLY reduce the life expectancy of the drive.

Thirdly, and not the least, it assumes that the hard drive is operable so as to run the software on it in the first place. If you have a hard drive that is smoked, and it has sensitive information on it, you don't want to just throw it away. That information is still on it, and can be retrieved, though again it will take extensive efforts to do it. If the information is sensitive enough, that can be a concern.

Truly the only way to ensure that this information cannot be retrieved is to destroy the hard drive. I mean, please...hard drives are just not that expensive these days, and if you're going to go through all that effort to wipe the hard drive and sell the computer, the fastest and easiest way to ensure that your data is secure and cannot be retrieved is to take the old one out and put a new one in. And you never know...you may find that, with a brand new hard drive and fresh OS installation, that old computer isn't as clunky as you thought it was.

There have been several valid ways to destroy the old hard drive presented. Yes, destroying it with a hammer carries with it the danger of being injured by flying debris, but so does driving a nail. Some of the methods are, shall we say, "whimsical" but not practical. There is one other method that hasn't been mentioned, though.

I used to work with a secure paper shredding company which had a huge machine that did the shredding. Among the things that this shredding machine did was...shred hard drives! That monster would take an entire hard drive and make mincemeat out of it. :-)

If the data on your hard drive is that sensitive (and you're that concerned about personal safety), look up a secure shredding facility in your area and take the hard drive to them. Secure Shredding facilities are generally government bonded (you have to have permission and either a badge or be accompanied to get into the shredding area), and if you have great concerns, they might even allow you to watch the hard drive being shredded.

Just another option.

Comment by Reagar on July 11, 2009 at 9:29pm: you know, you could always DBAN it a couple of times, its like virtually taking a hammer to the hard drive, that way they data is gone, and the hard drive is still useable. If you still have doubts, run Recuva and see how much data you can actually regain, if its 0, then congrats, the hard disk is as good as hammered.

Comment by system001 on July 11, 2009 at 7:28am: Simply take it to one of the college science labs and place it in sulfuric acid. There simply will be nothing left.

Comment by Mark Hilton on July 11, 2009 at 6:22am: carefully take the disk apart and then braze the disk portion with a blowtorch till it's completely warped. (that's what i did with mine, great stress reliever too)

Comment by chip.black on July 11, 2009 at 4:06am: Wipe it clean with your favorite security program. Then open it up, make an ash tray or knick knack holder from the case and take a hammer to the disk. Then glue the pieces to the top of a car that's about to be lifted (with a magnet) and dropped into a crushing machine. Then take the cube they turn the car into, put it on a rocket and shoot it into the Sun. In a billion years when the Sun explodes your data will be safe.

Comment by David Myers on July 11, 2009 at 2:12am: I agree with Desmond. Do a DOD wipe with DBAN. It's almost virtually impossible to recover data from that unless you have a lot of time and money.

If you're really paranoid; you can do what Bren suggested and use a good hammer :)

Comment by LADYTECH on July 10, 2009 at 1:26pm: Do u work for the FBI? If that's the case let them figure it out. lol
Software should do the trick and so what if your not using the hd, smash it, bash it then trash it.