Dark data is the inactive or unused information stored across your...

https://wiki-dale.win/index.php/What_is_Garbage_In_Garbage_Out_in_AI_Data_Prep%3F

Dark data is the inactive or unused information stored across your systems—often making up 55% of all data. It increases storage and backup costs and raises breach risk if left unmonitored. Inactive data is a common target for ransomware attacks