Dark data is the information your organization collects but never uses — often...

https://wool-wiki.win/index.php/Dark_Data_in_Object_Storage_%E2%80%93_Why_Do_Buckets_Get_Out_of_Control%3F

Dark data is the information your organization collects but never uses — often up to 55% of stored data. This inactive data not only wastes storage and backup costs but also increases risks like ransomware exposure