Protect Your Data When You Sell Your Computer

Someone contacted me last Friday with some questions regarding selling a computer, and it made me realize that a tip on protecting your data before you sell your device would be a great idea.  Identity theft is a major problem, and it is important that you take the steps to completely remove your information before you sell a device, especially if you are selling to someone you do not know.

For a laptop or desktop computer, I recommend a two-step approach.  First, remove the data files from the device by deleting them or by doing a factory reset.  To delete the files, simply move them to the recycle bin or trash can and then empty it.  For a more secure approach, you can do a factory reset to restore your device to its "out-of-the-box" state.  Most computers will have built-in software to perform this operation, but you will have to follow the instructions in the user manual since each computer has a different process for starting a factory reset.  (Some manufacturers may use other terms, such as "System Restore" for this process.)  This process will delete everything on the drive and then reinstall Windows.

However, even a factory reset does not mean that your files are completely gone.  When you delete a file, the computer does not actually remove the data; it just marks that area of the drive as usable.  The files are still there, and they can still be recovered and pieced together.  The reinstall of the operating system will write new data over some of your files, but there will still be areas with leftover data.

To remove this data, I recommend using the free program CCleaner.  Along with many other tools, it contains a drive wiper that can wipe all the free space on the drive.  After installing, click on Tools and then Drive Wiper.  Choose Free Space Only (or if it is installed as a second drive on another computer, you can choose Entire Drive), the number of times you want data written into each area of the drive, and the drive or drives you want to wipe.  Click the wipe button, and let CCleaner go to work.  Depending on the amount of free space on the drive and the number of passes selected, this may take a substantial amount of time, so you may want to let it run overnight.

If you are selling a phone or tablet, you will also want to ensure your data is protected.  Fortunately, both iOS and Android have built-in settings to do this.  iOS devices will do this by either encrypting all data and deleting the encryption key or by overwriting all data on the device.  Simply navigate to Settings, then to General and Reset, and select the Erase All Content and Settings option.

With Android devices, the process is slightly more complicated.  You will need to encrypt your data before performing the reset.  (Avast recently conducted a study by purchasing 20 phones that had been wiped to factory settings and found that it could recover data even after the factory reset.)  First, set up a lock screen PIN or password by going to Settings, Security, and Screen Lock.  Then, go to Settings, Security, and choose Encrypt Phone.  You will be prompted to enter your PIN and respond to a warning message.

Now, you can do the factory reset.  Go to Settings, Privacy, and choose the Factory Data Reset option.  The phone will now delete the encrypted data along with the encryption key.