Dark data is all the information your company collects but never uses—about...

https://bravo-wiki.win/index.php/How_Do_I_Find_Dark_Data_on_a_NAS_Without_Breaking_Anything%3F

Dark data is all the information your company collects but never uses—about 60-80% of it just sits there. This inactive data takes up space, slows systems, and can waste up to $2.5 million every year