Dark data refers to the inactive or unused information stored by an...

https://www.tool-bookmarks.win/dark-data-is-the-information-organizations-collect-but-don-t-use-often-making

Dark data refers to the inactive or unused information stored by an organization, often making up 55% or more of all data. This hidden data increases storage and backup costs and creates serious risks like ransomware exposure since it’s rarely monitored