Dark data is the inactive or unused information stored across your systems,...

https://alexisqoem867.trexgame.net/dark-data-vs-cold-data-are-they-the-same-thing

Dark data is the inactive or unused information stored across your systems, often making up 55% of all data. It poses a real risk by increasing exposure to ransomware and breaches and drives up storage and backup costs, sometimes wasting millions annually