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

https://www.bookmarking-planet.win/dark-data-is-the-inactive-or-unused-information-that-accumulates-in-your

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