Dark data is the information your company collects but doesn’t use, often...

https://www.slideserve.com/aaron_ward92/why-does-dark-data-create-operational-drag-for-it-teams

Dark data is the information your company collects but doesn’t use, often making up 55% or more of your stored data. It increases storage and backup costs and raises breach risk since outdated data can be a prime target for ransomware