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

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

Dark data is the inactive or unused information that accumulates in your systems—often 60-80% of stored data. It poses real risks like ransomware exposure and breach vulnerability since outdated files may lack current security controls