The most common way to act when we want to erase information, either loose files or on a USB, is to use the delete commands or select the item to be deleted and press the delete key, and empty the recycle bin to delete the files, format the device or throw the device containing the information in the trash when it stops working.

However, none of these forms of deletion can be considered secure because the information is not really completely deleted. With the right tools, it is possible to recover data from a formatted device or a deleted file, even after emptying the recycle bin.

Why is not all information deleted when we use any of these options?

Operating systems store information in files, and when the file is saved, its location is also noted in a database or file list. This list is the index that is used to then be able to find the contents of the files within the device.

When we use the delete method of the operating system itself as the “delete” key, the files are deleted only from the file index but the file content is not really deleted, it remains in the storage area until the space is reused with A new file.

When we format our hard drive or USB, we only overwrite the file list area, but the content with the information really remains intact. If we throw a device in the trash, even if it doesn't work, it keeps storing the information and in one way or another it can be recoverable and accessible.

Therefore, all the action that does not entail the elimination, both of the information in the file list and of the contents thereof, does not effectively destroy said information.

These ARE NOT methods of secure destruction: The operating system deletion commands access the file list and mark the file as deleted, but its contents remain intact.

So, how can we erase the information in a secure way?

The secure erase methods that prevent data from storage devices from being recovered once they have been deleted are demagnetization, destruction and overwriting.

Demagnetization and physical destruction do not allow the device to be reused later.

In demagnetization the support is exposed to a magnetic field with a power that will vary depending on the size of the device, while in physical destruction the support is physically removed completely.

Overwriting can be used on all rewritable devices (hard drives, USB, etc.) and consists of writing data about the data already contained in the devices.

In these 2 ways we can ensure that the information has been deleted properly and is unrecoverable.