Dark data is the inactive or unused information your company stores but doesn’t...

https://romeo-wiki.win/index.php/Why_Does_Dark_Data_Create_Operational_Drag_for_IT_Teams%3F

Dark data is the inactive or unused information your company stores but doesn’t analyze or manage. It can make up 60-80% of your data, leading to wasted storage and backup costs. Plus, it increases your risk of ransomware attacks and data breaches