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

https://www.bookmarkingtraffic.win/dark-data-refers-to-stored-information-that-is-not-actively-used-or-analyzed

Dark data is the inactive or unused information that piles up in your storage—often making up 60-80% of total data. It increases costs by wasting storage and backup resources and raises breach risks since outdated files can be vulnerable to ransomware