Dark data refers to information your company collects but never uses—often...

https://wiki-nest.win/index.php/Tiering_vs_Archiving_%E2%80%93_What_Is_Safer_for_Inactive_Data%3F

Dark data refers to information your company collects but never uses—often making up 55% of stored files. This unused data takes up space, drives up storage and backup costs, and increases ransomware risk since it’s often unmonitored