Dark data is the inactive or unused information organizations keep but don’t...

https://www.nav-bookmarks.win/dark-data-is-the-55-of-your-stored-information-that-s-never-accessed-or-used

Dark data is the inactive or unused information organizations keep but don’t analyze—often 55% of stored data. It increases storage and backup costs and raises ransomware and breach risks since attackers target forgotten files