Dark data is the inactive or unused information stored in your systems—often...

https://wiki-room.win/index.php/Agentic_AI_Risks:_What_Happens_When_Agents_Read_Old_Files

Dark data is the inactive or unused information stored in your systems—often 55% of all data. It increases storage and backup costs, sometimes wasting millions annually, and can expose you to ransomware or breach risks