A computer system that mails bills for some of Mid-Michigan's largest health care providers has been hit with a ransomware attack.
McLaren Greater Lansing is just one customer of Wolverine Solutions Group.
The company's President says the attack happened last September and affected several servers, one of which contained personal client data.
WSG said names, addresses, dates of birth, social security numbers, insurance information, and medical records were included in the files encrypted during the ransomware attack.
Blue Cross Blue Shield of Michigan says about 100,000 Michigan customers were impacted by the breach.
Based on an internal investigation, WSG says it believes the hackers only encrypted the files and never stole them off the company’s servers.
Patients affected will get a letter in the mail.
WSG said it started mailing out notices on Dec. 28 to impacted patients and will continue to do so through March.