Secure data deletion

Removing data stored on storage media (hard disk, memory stick, etc.) can be useful in many situations. Unfortunately, moving or deleting a file to the Recycle Bin does not mean that the file has been completely deleted, because in this case it can still be recovered. Emptying a recycle bin and conventional deletion also only make it more difficult to find the data again.

The transfer and disposal of hard disks or USB sticks can therefore be problematic, as there may still be sensitive data on the device or storage medium. Potential misuse scenarios include identity theft, the unwanted or unauthorized transfer of sensitive data to third parties, or the associated outflow of access data, which allows unauthorized access to computer systems or online banking environments. The misuse of sensitive data can be prevented or at least greatly hampered by secure erase (also known as secure erase, shredding or wiping). Before secure deletion, it is sometimes advisable to secure the data in encrypted form, as it will no longer be available. 


The respective procedure differs depending on the underlying operating system (Android, iOS, Mac, Linux, Windows, Windows Phone etc.), depending on whether the deletion of individual files or complete drives is necessary, depending on the storage medium (CD, DVD, hard disk, SSD, USB stick etc.) and the end device used (computer, smartphone etc.).

Normal deletion: A normal removal of data deletes a so-called index (the table of contents of a storage medium) and enables the release of this storage area. This means that although the data is still stored on the storage medium, it can no longer be found by the operating system using standard methods and can be overwritten with new data.

Tools for data deletion: Professional deletion includes the removal and (e.g. multiple) overwriting of data. The removal of single files or folders under Windows is easily possible with the program “Eraser”. In addition, CCleaner – for Android, Mac and Windows – allows the deletion of complete drives as well as the removal of temporary contents and registry files. For SSD drives it is recommended to use manufacturer-specific tools such as Corsair, Intel, Samsung and SanDisk. Under Mac both “Disk Utility” and “MacClean’s File Eraser” allow the deletion and formatting of a complete disk. However, Apple points out that the methods used for SSD disks do not provide sufficient protection.

Possible alternatives to deletion: On the one hand, the maximum possible physical destruction (drilling, breaking, cutting, scratching etc.) of a storage medium is a possible alternative (CD, DVD, USB stick, hard disk etc.), on the other hand encryption methods with long or complex passwords and long key lengths can also be used. For Macs, for example, the “FileVault” program offers such a solution.

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