by Dave Moore, CISSP
09/18/2022
Let’s compare your computer’s hard drive to a book, a printed book like you would get from the library. Remember, when we refer to “computers,” we mean all computers, including phones, iPads, laptops, the works, because they all have microprocessors, memory, an operating system, and, the subject of this section: information storage.
Your hard drive, being like a book, has different items on it that function like a table of contents, listing every single bit of information there. The information, organized into “files (documents, spreadsheets, songs, pictures, etc.) is made up of zeros and ones, as explained earlier, and those things actually occupy a physical space on the drive, whether it’s a magnetic platter or solid-state drive; the data has an actual physical location on the drive.
On many systems, when you “delete” a file, the file is actually still there, in its same physical location, only now it has a slightly different name. The different name tells the system it is now OK to put new zeros and ones in that space, but until new information comes along and actually occupies that space, the file is still there, and can be recovered.
Compare it to a library book. Let’s say I come along with a pair of scissors and cut Chapter Four out of the Table of Contents. Has Chapter Four disappeared? No, it’s still in the book; all I’ve done is remove it from the Table of Contents.
That’s what it’s like when you delete a file from most computer systems. All you’ve done is put it in the Trash, or the Recycle Bin. Even if you empty the Recycle Bin, reformat the drive and reinstall your operating system, the file is still on the drive until something else comes along and write a new set of zeros and ones in its place.
If you are going to sell, give away, or throw away a computer, these are things you need to pay attention to. You want to get rid of all personal, medical, private, financial and every other kind of information that relates to you. “Deleting” files won’t get the job done; you actually need to “erase” the files, removing them completely and permanently from the system.
One way to make sure you are not getting rid of your private information in a dumpster, only to have a bad guy come along and retrieve it, is to keep it. Remove the hard drive, and recycle the rest. Hard drives don’t take up much space, so just put it in a drawer or on a shelf closet, and get rid of everything else.
Some drives, especially spinning platter drives, can be erased and reused. Many organizations, and some individuals, will do this to save on the cost of buying new hard drives. I’ve done it myself, many times. This can be a do-it-yourself project, but it must be done properly. One of the most popular, and free, hard drive erasing programs is DBAN (Darik’s Boot and Nuke). Solid-state drives are the most difficult to erase and, if not done properly, can render the drive useless.
The most effective and thorough method is to physically destroy the hard drive, and, when I say destroy, I mean destroy.
Some people think hitting it with a hammer will get the job done; it won’t. Running over it with your car won’t work, either. Most medium-to-large sized cities have a company that specializes in document and data destruction, and they will usually have a machine called a hard drive shredder. The drive will be shredded and turned into small, useless chunks of metal.
Some shredding services will charge $5-10 per drive. Some recycling centers will do it for free if you let them keep the metal for recycling. No matter which way you go, ask to personally witness the shredding of the drive, just to be sure.
Next week: Step Twelve: Careful where you click!
Dave Moore, CISSP, has been fixing computers in Oklahoma since 1984. Founder of the non-profit Internet Safety Group Ltd, he also teaches Internet safety community training workshops. He can be reached at 405-919-9901 or internetsafetygroup.org