S-U-P-E-R.ch – How to properly delete data that is no longer needed

18.09.2023 - Backing up data is not the only important thing. If information is no longer required, it should be properly deleted or destroyed. However, «deleting» is not the same as «permanently deleting». Deleting data is generally a multi-stage process, as electronic data is not completely removed when it is deleted with the delete key or the delete function. To delete data permanently, the storage location of the information must be repeatedly overwritten.

If you select a file and click on delete, the file is merely moved to the recycle bin and can be restored from there. Emptying the recycle bin only deletes the file reference from the file system table, and not the file itself. This means that the space it occupied is marked by the system as available for overwriting, but the data itself is not overwritten and can be restored.

This deletion principle also applies to other storage media such as external hard drives. With normal formatting, only the file system structure is deleted, and the files themselves remain on the storage medium until they are overwritten.

Special programs are available to permanently destroy data. This process is also called wiping.



  • Windows: delete your data/files with the free programs CCleaner or File Shredder.
  • MacOS: delete the files on the computer as usual. Open the Trash (equivalent to recycle bin) and select «Secure Empty Trash».
  • External hard drives: use the free Eraser tool to wipe the data on your hard drive in a way that makes it irrecoverable.

Smartphones and tablets:

On modern Android and Apple devices, the storage space is encrypted if the corresponding function is available and enabled. It is therefore sufficient to delete the associated key to prevent access to the data. This is done by restoring the device to factory settings. However, how secure this procedure is also depends on the encryption algorithm and key used by the manufacturer. Therefore, it makes sense to additionally overwrite (wipe) the data with a special tool. Overwriting the data is also the only option for older devices that do not have encrypted memory. If memory cards are used, they too must be overwritten several times.

Further information

Last modification 18.09.2023

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