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

https://www.hotel-bookmarkings.win/dark-data-is-the-information-your-business-collects-but-never-uses-often-55-of

Dark data is the inactive or unused information stored across your systems, often making up 55% of all data. It poses a real risk by increasing exposure to ransomware and breaches and drives up storage and backup costs, sometimes wasting millions annually