Dark data is the inactive or unused information your business stores but...

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

Dark data is the inactive or unused information your business stores but doesn’t analyze, often making up 55% of all data. It creates real risks like increased ransomware exposure and drives up costs through wasted storage and backup resources