Mid Michigan Medical Billing Service Reports Ransomware Attack, Data Breach
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Mid Michigan Medical Billing Service (MMMBS), a revenue cycle management firm based in Flint, Michigan, reports a ransomware attack that compromised the data of over 28,000 patients. The company discovered the breach in March 2025.
The Qilin ransomware group claimed the attack and apparently stole approximately 38 GB of sensitive files. They listed MMMBS on their dark web leak site and threatened to publish the stolen data if the company did not pay the ransom. The stolen data includes:
- Full names and dates of birth
- Social Security numbers and driver’s license numbers
- Medicare and Medicaid identification numbers
- Diagnosis and treatment information
- Medical record and patient account numbers
- Health insurance and payment card details
- Employer identification and passport numbers
- Biometric data and treating provider names
The incident affected 28,185 individuals.
MMMBS hired security experts to investigate and notified law enforcement and business partners to contain the damage. MMMBS reported the incident to the U.S. Department of Health and Human Services on January 5, 2026. The company is offering free credit monitoring to the affected individuals.
