Dark data is the inactive or unused information that sits in your storage—often...

https://technivorz.com/how-do-i-stop-dark-data-from-polluting-our-ai-search/

Dark data is the inactive or unused information that sits in your storage—often 55% of all stored data. It not only wastes resources, driving up storage and backup costs, but also increases risks like ransomware attacks or data breaches