QotW #18: How can we destroy data on a hard drive?

2012-02-16 by . 0 comments

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Rather than focus on a specific question this week, we have 9 questions related to the destruction of data, 5 of which are specifically interested in destroying hard drives, as in this modern age where everything is recorded, there are good reasons for ensuring data is deleted when required.

So this post will concentrate on destroying the the drive itself. For the deletion of data from a storage device, have a look at our blog post for Question of the week number 4: How can you reliably wipe data from a storage device?

Matthew Doucette asked simply: How do you destroy an old hard drive?

To which Scott Pack produced the following incredibly detailed answer:

When it comes to drive destruction you typically see one of two main fields:

  1. Disk Degaussing
  2. Physical Destruction


Degaussing used to be the norm, but I am not such a big fan. On the plus side it is fast, you’ll normally just dump the disks on a conveyor belt and watch them get fed through the device. The problem is auditability. Since the circuitry is rendered wobbly, you won’t be able to do a spot check of the drives and verify that the data is gone. It is possible, with some level of probability unknown to me, that data could still exist on the platters. Retrieving the data would, without question, be difficult, but the fact still remains that you cannot demonstrate the data is actually gone. As such, most companies now will actually be doing physical destruction.

Physical Destruction

At the low end, say a small box of drives at a time, you’ll have hard drive crushers. They’re often pneumatic presses that deform the platters beyond useful recognition. At the risk of supporting a specific product, I have personally used this product from eDR. It works well, and is very cathartic.

At a larger scale, say dozens or hundreds of disks, you’ll find large industrial shredders. They operate just like a paper shredder, but are designed to process much stiffer equipment. The mangled bits of metal that are left over are barely identifiable as hard drives.

At an even larger scale you can start looking at incinerators that will melt the drives down to unidentifiable lumps of slag. Since most electronics can produce some rather scary fumes and airborne particulates, I would not recommend doing this on you own. No, this is not a good use of your chiminea.

Manual Dis-assembly

If you are dealing with one or two drives at a time, then simple dis-assembly might be sufficient. Most drives these days are largely held together with torx screws, and will come apart with varying levels of difficulty. Simply remove the top cover, remove the platters from the central spindle. Taking a pocket knife, nail file, screwdriver, whatever, have fun scoring both surfaces of each platter. Then dispose of the materials appropriately. I cannot speak to how recoverable the data is afterwards, but it is probably sufficient. The biggest thing to keep in mind is that while most desktop hard drive platters are metal, some are glass. The glass ones shatter quite extravagantly.

Additional Considerations

Before you decide on a destruction method, make sure to identify what kind of data is stored on each device and treat it appropriately. There may be regulatory or legal requirements for information disposal depending on what data is stored on the disk. As an example, see section 8-306 of DoD 5220.22-M.

For hard drive destruction, DoD 5220.22-M section 8-306 recommends: “Disintegrate, incinerate, pulverize, shred, or melt”

All that being said, performing a single pass zero wipe is probably sufficient for your purposes. Modern research indicates that modern hard drives are largely immune to the “magnetic memory” problem we used to see on magnetic tape. I would never bother doing anything more on a household drive unless the drive itself was exhibiting failures

Ryan M asked a very similar question – What is the best method of retiring hard drives?

And Scott also gave these 2 excellent points in his answer:

Electrical Scrambling

In the olden days when you had a room packed with tape there were few things better than a big honkin’degausser for making sure that you knew what left the room. As hard drives supplanted tape, their use simply got transferred to the new medium. The biggest advantage to using a degausser to take care of hard drives is speed. Just pass a box through the unit, ignore the jiggling in your fillings, and walk away with clean drives. The downside is the lack of ability to audit data destruction. As discussed in the Wikipedia article, once a hard drive is degaussed, the drive is mechanically unusable. As such, one cannot spot check the drive to ensure cleanliness. In theory the platters could be relocated to a new device and we cannot state, categorically, that the data will not be accessible.

Wanton Destruction

This is without question my favorite. Not only because we demonstrate, without question, that the data is gone, but the process is very cathartic. I have been known to take an hour or so, dip into the “To Be Destroyed” bin, and manually disassemble drives. For modern hard drives all you need is a torx set and time (possibly pliers). While one will stock up on their magnet collection, this method of destruction is very time consuming. Many companies have developed equipment specifically for hard drive destruction en-masse. These range from large industrial shredders to single unit crushers such as this beauty from eDR. I have personally used that particular crusher, and highly recommend it to any Information Security professional who has had a bit of a rough day.

I’m thinking if I ever need to destroy hard drives, I’ll either blow them up / give them to my kids / use them for target practice or ask Scott to have fun with them.

Dan Beale points out that exactly what approach you take depends on:

  • how sensitive is the information
  • how serious are the attackers
  • do you need to follow a protocol
  • do you need to persuade other people the data has gone

Auditability is essential if you are susceptible to regulations around data retention and destruction, and for most organisations this will be essential around regulations such as the Data Protection Act 1998 (UK), GLB or HIPAA (US) and others.

Filed under Data Standards

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