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

https://www.paste-bookmarks.win/dark-data-is-the-information-your-organization-collects-but-doesn-t-use-often

Dark data is the inactive or unused information that piles up in your storage—often making up 55% of all enterprise data. This unused data increases costs through wasted storage and backups, and it raises your risk of breach or ransomware exposure