Have you ever sold an old computer? Given it to charity? Or sent it to the scrapheap? If so, you could be among thousands of Brits who may have unwittingly put their personal data at risk in the process.

It’s a common misconception that ‘delete’ means ‘destroy’. In fact, with just a little expertise, deleted files can easily be recovered from old hard drives.

In an investigation conducted by Which? Computing, we purchased several second-hand hard drives online via eBay – some cost as little as £15 to pick up.

Using the kind of data recovery software that can be cheaply downloaded off the internet by anyone, we were able to recover over 2,500 files from the eleven hard drives we’d purchased. We recovered everything from personal photos, spreadsheets, music files to online chat conversation histories.

Our lab experts conducted this exercise under tightly-controlled conditions, and the recovered data was fully destroyed at the end of the investigation. But in the wrong hands, the same data could lead to ID theft, fraud or even blackmail.

The risks of recovered data

Have you ever saved a CV on to your computer’s hard drive? Ever done your online banking on your home computer, or saved copies of documents to do with your home finances? These are exactly the sorts of files that can be retrieved from an old hard drive if all precautions aren’t taken to destroy the data properly.

In our recent survey of 1,003 Which? readers, we found that many are potentially leaving themselves at risk when disposing of old computer equipment. Of those who had ever sold or recycled a computer, 53% deleted their files first, though only 38% said they’d emptied the Recycle Bin as well.

Crucially, only 43% of the respondents had removed a computer’s hard drive before disposing of it. When you’re dealing with your own private files, this is the most secure method of all for ensuring no one can recover your own data from your old computer.

Data destruction – how do you do it?

Keeping a library of old hard drives stored away at home may seem like a pain, but it beats the risk of leaving your files on an old hard drive when disposing of an old computer.

Alternatively, data-wiping software can help to permanently over-write your files, though this can often be complicated to use for the less computer-savvy.

The safest method of permanent destruction is to remove a hard drive and take a hammer to it until the disk is smashed to smithereens. Environmentally this isn’t great, and it can prove hard work, but it certainly makes things nigh-on impossible for data thieves.