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

https://source-wiki.win/index.php/How_Do_I_Find_Dark_Data_on_My_NAS_Without_Breaking_Anything%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