Dark data is the inactive or unused information that accumulates in your...

https://wiki-quicky.win/index.php/How_Do_I_Move_Cold_Data_to_Cheaper_Storage_but_Keep_Access%3F

Dark data is the inactive or unused information that accumulates in your systems—often 60-80% of stored data. It poses real risks like ransomware exposure and breach vulnerability since outdated files may lack current security controls