Making a Hard Drive Unreadable


Today’s Question: How can you make sure that a hard drive has been erased so nobody can recover data from it? And how do you wipe your old internal drives when they are no longer in a computer, but sitting in a drawer?

Tim’s Quick Answer: If a hard drive is still usable, you can easily format the drive with a security option that will wipe the data so that nothing can be recovered. If the drive is no longer usable you can physically damage the drive to prevent data recovery.

More Detail: Both the Windows and Macintosh operating systems include options for securely erasing a hard drive. This involves not only erasing data from the drive but also writing random data back to the drive so that the original data cannot be recovered.

On Windows you can use the Format command using the Command Prompt application. On the Start menu look for the Windows System folder, and within that folder launch Command Prompt. You can then type the Format command for the drive letter you wish to delete all data from, including the “/P” parameter to have multiple passes of meaningless data written to the drive. The more passes you use the more secure the erasure will be.

For example, let’s assume you have a drive with drive letter Z: assigned to it, and you wanted to use four passes to overwrite the drive. You would use this command at the Command Prompt:

Format Z: /P:4

Macintosh users can use the Disk Utility application, which is found within the Utilities folder in the Applications folder. Select the drive you want to erase, and then click the Erase button. In the Erase dialog you can specify the Name you want to use for the drive, as well as the Format you want to use for that drive. More importantly in this case, you can click the Security Options button and drag the slider to the “Most Secure” setting before clicking OK. Then click the Erase button to securely erase the data from the drive.

If the drive is no longer usable you can take steps to physically disable the drive. One simple way to achieve this is to damage the circuit board on the drive. You will likely need a special Torx screwdriver to remove the circuit board, in which case you can carefully break the circuit board in half. If you’re not able to remove the circuit board, you can simply damage the board directly.

Damaging the circuit board will prevent the hard drive from being used as-is, but it won’t actually remove the data from the drive. If you want to render the drive unreadable you would need to damage the platters in the drive (or the flash chips for SSD drives). There are various techniques you could use to physically damage the drive, but you’ll want to be very careful to avoid injury. If you’re able to open the drive and get to the platters, you can physically damage those platters, but again you’ll want to exercise caution here.

Unless you have highly confidential data on your drives, it may be overkill to try to physically destroy the drive. Instead, I suggest wiping the drive through the operating system if possible and also carefully damaging the circuit board.

You can then take advantage of a hard drive recycling program, which offers to destroy your drive without accessing your data. Western Digital offers this type of service, which you can learn about here: