Completely erase a hard disk

If you’re thinking of selling your computer, giving it to a friend, or simply re-using it without fear of your data falling into the wrong hands, then you’ve come to the right place. We’re going to show you different ways of erasing all the data on your hard disk for good.

Erasing your hard disk : Fast or deep formatting ?

When the time comes to clean up your hard drive, whether to revitalize an old computer or to prepare your PC for a fresh start, it’s best to choose the most appropriate erasing method. Should you opt for fast or thorough formatting? Here’s what you need to know:

Quick formatting

Quick formatting is a fast, efficient way of erasing data. This method is ideal for reinstalling an operating system or freeing up space on a hard disk. However, it is important to note that this method does not completely erase data, and leaves residual traces that can be recovered by data recovery software. Consequently, this method is not recommended if the disk contains sensitive data.

In-depth formatting

Deep formatting, or low-level formatting, is a more exhaustive procedure and is recommended when confidentiality of information is crucial. This method erases data more completely, reducing the risk of data recovery. However, it may be excessive for simply erasing free areas of a hard disk without sensitive data.

Data formatting methods

Several formatting methods have been developed to irreversibly erase data, making any attempt to recover or inspect it virtually impossible.

• The Gutmann method is considered the most effective. Using 35 erasure passes, it uses different combinations of bits to mask the original recording as much as possible and render any attempt to inspect areas of the disk illegible. On the other hand, it is painfully slow, taking around 24 hours for a 1 Terabyte hard disk.
• The US DoD 5220-22.M /E, C and E method performs 7 erasure passes. Designed by the U.S. Army, it is often judged to be sufficient and faster than Gutmann.
• The US DoD 5220-22.M /E method is a lighter version of its predecessor, requiring just 3 passes. It is resistant to most “magnetic reactivation methods” and is therefore a fast, high-performance eraser.
• PseudorandomData is a 1-pass method considered well-suited to deleting free disk areas or erasing information on compressed volumes. It resists the usual file recovery and hacking methods.
• Only First and Last 2KB is a very fast but not very effective method. It prevents file restoration software from restoring office or image files to their original state, but is not resistant to any advanced method.
• Schneier’s 7 Pass is an equally robust erasure method based on 7 passes. Designed by Bruce Schneier, one of the world’s leading experts in security and encryption, this method (presented as highly effective by its author) remains controversial.

Permanently erase data with the PseudorandomData algorithm

The PseudorandomData single-pass method is widely regarded as an effective data erasure method. It is resistant to common file recovery and hacking techniques. To implement this method, we’ll be using Eraser, a free, open source tool designed to securely delete sensitive files and data by repeatedly overwriting them. Let’s get started!

1. Download the latest version of Eraser.
2. Once the download is complete, double-click on the file to start installation.

3. Accept the software’s terms of use.

4. Click on the Complete button.

5. Then click Install.

Once the software is installed, launch it.

• In the Eraser window, right-click and select New Task.

Then click on Add Data.

1. In the new Target type window, choose Drive / Partition.

Under Settings, select the hard disk to be erased. Make sure you choose the right disk, as this operation is irreversible.

1. In the Erasure method list, select the PseudorandomData formatting method.

1. Click OK to confirm the task parameters.
2. Select the Run immediately box, then click OK.

Eraser will start overwriting all data on the external hard disk using the PseudorandomData method. The time required will depend on the size of the hard disk, but this method is generally faster than some of the more complex methods.