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What You Need To Know About Data Deletion Before Selling Your Old Computer

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Most consumers buy new hardware regularly — a new PC for instance that is replacing the old one, preferably faster and with more hard drive space, or a new digital camera or cell phone.

But what about the old hardware? You could of course give it to family members or close friends, but what if there isn't anyone who would want it? Selling the hardware on a site like eBay could be the solution then. Making a few bucks from used hardware that is no longer needed is a great deal for anyone, right?

What most users don't know is that they can run into trouble when selling used hardware. The reason is simple — data that is stored on those devices might still be accessible. Even users who think they have deleted the data thoroughly might be in for a surprise if a tech-savvy friend points it out to them. Or if they find out later that the buyer decided to publish private documents, pictures or videos on the Internet.

Computers have hard drives that store the data. Most consumers think that formatting the hard drive is enough to delete the data so that it cannot be recovered. That, however, is far from the truth. It becomes even less obvious with devices with built-in storage, digital cameras for instance, or cell phones. Those contain data as well and many consumers do not delete the data before they sell the device. That's a huge privacy problem. Data that is not deleted can be accessed by the new owner immediately but many do not know that it is also possible to recover deleted data with the right tools.

Data Deletion 101

Whenever you delete data in an operating system it is not deleted physically from the device. The operating system simply marks the area where the data is stored as writable and deletes the file information that is pointing to that area. This means that the data is still there and that it can be recovered with the right tools.

Why does the operating system do it this way? The simple answer is that it is faster to simply delete the file pointer and mark the data as writable.

Wiping Data

Securely deleting data is often referred to as wiping data. This process ensures that it becomes impossible to recover the data that was stored on the devices.

Wiping, unlike normal file deletion in the operating system, overwrites the area on the hard drive or device where the data was stored, making it impossible to recover it.

There are several processes (tech savvy users call them algorithms) that process the data, from overwriting the data with 0s to military grade algorithms that overwrite the data up to 30 times.

There is no real benefit in using advanced methods of wiping files as it has been tested time and time again that data is not recoverable by normal means after being overwritten with 0s.

The efficiency of the deletion can easily be judged by running a file recovery software like Recuva on the device to see if the data can be recovered.

Disk Wiping Software

Devices like digital cameras, external hard drives or cell phones can usually be connected to a computer. Specialized programs can then be run on the computer to erase the data completely. One such tool is Eraser, a free program that erases data. It is available for the Windows operating system and can be used to permanently delete the data on the drive (with the exception of the main Windows drive).

An alternative to Eraser is Darik's Boot and Nuke. It needs to be burned to CD and run during system boot. Windows is not loaded at all which makes it possible to delete the system partition with Windows as well.

There are other free tools available on the Internet that can be used to delete data on devices permanently but those two are more than sufficient for most tasks.

It is highly recommended that you delete the data securely and permanently before selling or giving away devices with storage capacities. After all, we do not want to risk seeing private data leaked on the Internet.

Using Eraser to Delete Data Securely

Eraser is an open source program for the Windows operating system that can be used to make it impossible to recover deleted data on hard drives and external storage devices. The program is very easy to use and suitable for users of all experience levels.

Start the application after installation. Each Eraser task needs to be scheduled in the program. To create a new task click on the New Task link or press Ctrl N.

The Task Properties window will pop up. In here you can define the task type and how it should be scheduled. It is for instance possible to create a manual task or one that will be executed once a week.

Keep the default options for now and click on the Add Data link in the lower left corner of the Task tab.

This new window defines which data should be deleted securely. Eraser offers to delete a selected file, files in a specified folder, the recycle bin or the unused disk space on a drive.

  • File: If you want to delete a single file so that it cannot be recovered
  • Files in a folder: If you want to delete the contents of a folder
  • Unused disk space: Will overwrite the free data on the selected hard drive so that the data cannot be recovered
  • Recycle Bin: Overwrites the data stored in the recycle bin

It is generally recommended to uninstall software first, then delete files or folders, and finally run the unused disk space task to ensure that all data on the drive that has been deleted cannot be recovered.

The newly configured task should now appear in the Erase Schedule list of Eraser. Since it is a manual task we need to start it by right-clicking it and selecting Run Now. This can be repeated whenever it is necessary.

It can take some time to finish the wiping of data. Eraser by default overwrites the unused disk space with random data and uses the Gutmann algorithm for the deletion of existing files. Both methods can be changed in the options of the program which can be accessed by clicking on the Settings button.

It is recommended that you run a file recovery program after Eraser to ensure that the data has been deleted completely from the system.

Non-Deletable Media

What about non-deletable media like CDs or DVDs? It is possible to store them in a secure place or to use a CD shredder to destroy the CD or DVD physically. Amazon carries several CD shredders like the Fellowes 32177 Powershred PS-77Cs Shredder which can make CDs and DVDs unrecoverable.

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About Cindy Simson

  • Ruvy

    Thank you for this article, Cindy!!

  • Brian aka Guppusmaximus

    Great Article…

    But, I think you should have included a section about the Dept. of Defense regulation on wiping (which is seven passes). I believe there is still a debate on whether or not one pass would be successful with the newer HDD technology.

  • Cindy

    Thanks guys. Brian, when you say newer HDD technology do you mean SSD?