Securely & permanently delete data: smartphone, hard drives & co.

Sensitive data should be securely deleted when it is no longer needed. Data should also be removed from smartphones, computers and the like before they are passed on so that unauthorised persons cannot access them. However, a click on ‘Delete’ is not enough.

Deleting data securely from hard disks and flash memory

Mostly, data is simply moved to the recycle bin and this is emptied occasionally. However, the files ‘deleted’ with a mouse click can still be found on the device, only their reference has been deleted. Therefore, they can be restored. For data to be really removed, they usually have to be overwritten.

• On a hard drive, data is irretrievably deleted by overwriting. There are special programmes for this purpose such as Eraser, Secure Delete and File Shredder. All three can be downloaded free of charge.
• If the disk is defective anyway and should be disposed of, you can simply destroy it thoroughly mechanically. Be careful, however, as it may splinter.
• For flash memories, the ATA command ‘Enhanced Security Erase’ is recommended, which resets all memory cells. For this, you should use the corresponding tool from the manufacturer.
• You cannot safely erase these memories by overwriting them. However, if the medium is no longer needed, you can destroy it mechanically. Then unscrew it to check whether all the memory blocks are really broken.

Remove data securely from your smartphone

With smartphones, it depends on your device whether and by which method data can be safely removed. If in doubt, it helps to contact the manufacturer.

• Before the deletion process, you should back up all the data you still want on an external medium and remove the memory and SIM cards.

• If your mobile phone has an encryption function, you should use it now. The data can then only be decrypted with the appropriate code, which already offers significant protection.

• If you have an older model, it probably does not have an encryption function. You can then simply overwrite the data by copying harmless large files onto your phone.
• Finally, the smartphone should be reset to the factory settings in both cases. You can usually find out how to do this from the operating instructions for your mobile phone. Otherwise, you can also contact the manufacturer.