Data Protection (Part 2) - Securely Erasing a Drive

Yesterday we reported that, quite worryingly, many people don’t securely erase their data when they sell their hard drive. A study by Blancco Technology Group found that 67% of the 200 drives they purchased still had personal information that was retrievable.

Increasingly, people are storing more and more of their lives on their hard drive, with all manner of information including bank details, passwords, scans of ID and family photos being accessible to anyone with a basic knowledge of data recovery.

The process of removing data permanently from a drive is known as ‘sanitisation’, and it is important to remember that dragging files and folders to the recycle bin won’t achieve this, nor will formatting. Using default commands like Disk Management on Windows machines and Disk Utility on Macs doesn’t actually overwrite the data on the drive; the pointer to the data is removed. Index files stores and updates a listing of where on the drive each file is located. When the file is deleted, the index entry is removed, but the file and its data remains. From the point of view of the file system, the file is no longer present on the hard drive, and the sectors containing the data are considered free space.

Until the operating system actually writes new data over the sectors containing the contents of the file, it’s still possible to recover it. There are tonnes of data recovery programs, many free, that can scan a hard drive and recover deleted files. If you are looking to sell your hard disk drive, destroying the drive obviously isn’t an option, so the next best thing is to use a disk wiping tool. With the data fully sanitised, even a hard drive data recovery expert will find it next to imposssible to recover your data. It goes without saying that you need to back up all your files first.

Disk wiping is a non-destructive way to permanently remove data from a drive, and there are dozens of tools out there. The one we recommend is Darik’s Boot and Nuke, or DBAN, a free data destruction program.

Because DBAN erases every single file on the drive and overwrites it with dummy data, it needs to be run while the operating system isn’t in use, by burning the ISO file to an empty CD, DVD or USB drive. Once DBAN has been burned to the bootable media, restart your machine and boot into it. Your machine should detect the program automatically and boot, but if it doesn’t, you may have to press a function key (normally F11 or F12, depending on the model) to bring up a list of drives to boot from.

Once you have booted into the DBAN screen, press Enter, which starts DBAN in interactive mode. This will allow you to select the drive you want to erase, which will typically be the C: drive, and not indiscriminately erase every drive connected. Highlight the drive you want to erase, and press space, which will bring up a [wipe] notification. Pressing F10 will begin the erasure process, and how long it takes will depend on the size of the drive. The program will show you how long it has been running the erasure, how long is left, and the percentage of the erasure so far. Upon completion, you will get a green Pass message.

You can download the program here.

hard drive data recovery