Dark data is the information your company collects but doesn’t use or manage....

https://seo.edu.rs/blog/dark-data-risks-what-security-teams-worry-about-11142

Dark data is the information your company collects but doesn’t use or manage. It often makes up 55% of data stored, leading to wasted storage and backup costs. Plus, it increases ransomware and breach risks since unmanaged data is harder to protect