When your hard drive is replaced, the previous hard drive is returned to Apple and refurbished. As part of the refurbishment process, Apple erases and reformats all hard drives to help address any concerns about data security or identity theft.
You might send your computer for repair when the hard disk is still working—either the drive works intermittently or your hard drive isn't the issue requiring repair. If you are concerned about data security and your hard disk is still functioning, you should back up your important data and use the secure erase functions in Disk Utility (described below) to reformat your drive before sending in your computer for service.
Secure erase functions in Disk Utility
Your erase options depend on which version of OS X you have on your computer.
- Mac OS X v10.4 and later includes additional secure erase options in Disk Utility.
- Mac OS X v10.3.x and earlier include a Zero all Data function in Disk Utility that you can use to completely erase the drive.
Note: With OS X Lion v10.7 or later and an SSD drive, Secure Erase and Erasing Free Space are not available in Disk Utility. These options are not needed for SSD because a standard erase makes it difficult to recover data from an SSD. For more security, consider turning on FileVault encryption when you start using an SSD. FileVault, available in Mac OS X v10.3 and later, prevents others from easily accessing any information contained within your Home folder, even if the drive unexpectedly stops working or is serviced.
Always remember to make a backup of your important data before using any erase or encryption options, as any rewriting of data includes a risk of data loss.