Dark data is the 55% of stored information that sits unused but still costs...

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

Dark data is the 55% of stored information that sits unused but still costs money to keep and backup. It can increase your risk of ransomware attacks since unmonitored data is an easy target