How to securely erase data from a hard drive

At Fields Data Recovery, we regularly purchase second-hand hard drives for spare parts. Over the last few years, we’ve noticed that more and more of these devices still contain data created by their previous owners. Granted, the users have nearly always deleted their data and the problem is therefore caused by naivety rather than neglect, but this doesn’t change the fact that the personal information present on the drives is still easily accessible and ripe for exploitation.

Many people assume that data is permanently deleted following them having emptied their recycle bins, but this is simply not the case. When this is done, the devices firmware is simply informed that the data is no longer required and that the location within which it is stored can be overwritten with new data if necessary. As a result, should someone simply delete the data contained on their hard drive and then sell their device, a person who was inclined to do so could retrieve the information the drive contained with relative ease.

Yes, the risk is relatively low but, with more and more cybercriminals now aware of the fact that second-hand computers and storage media are a potential goldmine of data, many are now actively purchasing such devices in order to exploit the information they find for personal gain. Individual users are therefore putting themselves at risk of identity theft whilst businesses – and you’d be surprised just how many fail to securely erase data before disposing of their drives – could be liable for some huge fines, particularly with GDPR having recently come into effect.

With this in mind, here are, in our opinion, the three best ways to ensure the data on your hard drive is erased:

Securely erasing files

We know it might look like we’re contradicting ourselves here, but whilst standard deletion techniques are insufficient, just as specialist software can retrieve data from a failed drive, it can also be used to erase it.

To cut a long story short, this software works by not just deleting references to the locations of data within the devices firmware but by also continuously overwriting it with random data thus ensuring that nothing a nefarious individual would find useful remains.

Sadly, this is the only technique on this list that, if utilised, will allow you to sell the drive on at a later date but there is an increased risk that a skilled cybercriminal could recover remnants of data if the erasure isn’t completed by someone who is completely au fait with the software in question.

Physical destruction

Whilst not entirely guaranteed to render the data held on a drive completely unreadable, it makes the task of retrieving it so difficult that very few cybercriminals – the vast majority of whom rely on low-hanging fruit – would even consider attempting it.

Yes, simply opening your hard drive and taking a hammer to its platters is an extremely secure and cost-effective means of erasing your hard drive but (and forgive us for stating the obvious) you certainly won’t be able to sell it on afterwards.

Magnetic degaussing

For businesses that don’t want to fall foul of GDPR and be issued with a gargantuan fine, as well as the security-conscious individual, magnetic degaussing is undoubtedly the very best way of erasing your data.

Put simply, a degausser completely demagnetises a hard drive’s platters and removes all of the data stored on it in the process. Following this, there is no way it can be recovered. 

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