A study by the UK's Information Commissioner's Office (ICO) has found that 11% of reused hard disk drives contain sensitive personal information about their previous owners.
Hard disk drives (HDDs) are present in most computers and are used for storing and accessing digital information. What many people don't know is that when a file is deleted from a hard drive, it isn't actually deleted, only the visible link to it is removed. Even when the recycle bin is emptied a recoverable imprint of the file remains.
Bang Goes the Theory
A recent test by the BBC's Bang Goes The Theory team found that even after some pretty destructive experiments data was often still recoverable on hard drives. You can check out the Bang website for further information.
What does it mean for you?
You should be aware that personal information will be present on your computer's hard drive, and that you should take steps to properly erase it if you intend to sell or dispose of your computer.
Don't assume that deleting that Word document you used to save passwords, emptying the recycle bin, formatting your computer or resetting it to factory defaults will actually remove anything. It won't; there will still be a recoverable imprint of your data on the hard drive.
What you can do to protect yourself
The bullet-proof method of deleting personal information is to physically destroy the hard drive. However, the more practical solution for the average person is to use secure data removal software.
Programs such as CCleaner and Eraser work by overwriting the original hard drive information many times, eventually removing the traces. They do not require the dismantling of the computer, nor expert knowledge. At their maximum security setting they can take a very long time to delete all your data, the benefit being that once complete it will be virtually impossible for your personal information ever to be recovered.
Following on from their study, the UK's Information Commissioner's Office have also published their own guidelines on how to securely delete information.