Dark data is the inactive or unused information that piles up in your...

https://telegra.ph/How-Do-I-Quantify-What-Dark-Data-Is-Costing-Us-Each-Year-07-20

Dark data is the inactive or unused information that piles up in your storage—up to 60-80% of it. This data not only wastes money on storage and backups but also increases your risk of ransomware attacks and data breaches