ISO 21964 / DIN 66399
The ISO 21964 standard (also known as DIN 66399) defines the different protection classes, categories of data carriers, and levels of security for the destruction of media containing confidential data.
With new technologies, it has become apparent that confidential data can be stored on multiple types of media (paper, hard drives, tapes, etc.) and that their destruction can be classified according to different levels of security defined based on the difficulty of reconstructing the information after the media is destroyed. The ISO 21964 standard classifies data carriers into 6 categories, each represented by a letter.

THE DIFFERENT MEDIA TYPES
DIFFERENT PROTECTION CLASSES
The ISO 21964 standard provides 3 protection classes: normal, high, very high. They determine the level of sensitivity of the data by classification (internal, confidential, or secret data) and allow everyone to know the level of security required for the destruction of their data.