If you are an attorney disposing of an old Mac, you should be sure that any confidential information is securely removed before doing so. The process outlined below can securely erase your hard drive, and the software enabling you to do so is included free as part of Mac OS X.
- Launch Disk Utility (/Applications/Utilities) and when the application opens select the drive you want to erase in the pane on the left side of the Disk Utility window.
- Click the Erase tab and then click the Security Options button below.
- You can choose one of the following four options:
- Don’t Erase Data :: Doesn’t erase any data but wipes out the directory that tells your Mac where your data is. Unfortunately, several third-party utilities can scour your drive and recover your data after you’ve employed this option. This option is not secure.
- Zero Out Data :: Writes zeros over your drive one time. While it’s not up to government standards, recovering data from this drive will be a chore.
- 7-Pass Erase :: Meets that US Department of Defense 5220-22 M standard, as it writes over your data seven times.
- 35-Pass Erase :: Goes even further by overwriting your drive 35 times to make your data super-mega-ultra-really gone.
Source: "Securely Wipe Your Hard Drive" by Christopher Breen, published at Macworld.com.