Horizon Behavioral Health Data Breach Investigation

Recently, Horizon Behavioral Health reported to the Attorney General of the Commonwealth of Massachusetts that it had experienced a data breach in which sensitive personal identifiable information and protected health information in its care may have been compromised. According to the breach notice, on March 16, 2025, Horizon Behavioral Health experienced a ransomware incident.¹ As a result, Horizon Behavioral Health launched an investigation to determine the nature of the incident.

Through its investigation, Horizon Behavioral Health confirmed that sensitive personal information in its systems related to insurance claims may have been viewed and obtained by an unauthorized third party between March 13 and March 16, 2025. As a result, Horizon Behavioral Health began a review of the data to determine what information had been impacted by as well as identify the specific individuals affected. While the information impacted varies depending on the individual, the type of information potentially exposed includes:

• Name
• Social Security number
• Address
• Zip Code
• Driver’s License number
• Date of birth
• Diagnosis/Conditions
• Medications
• Insurance Claims information

As a result of the breach, Horizon Behavioral Health began mailing data breach notification letters to impacted individuals and posted notice on its website. Based on the breach notice sent to Massachusetts residents, Horizon Behavioral Health is providing affected individuals with a list of the specific types of sensitive information impacted and complimentary credit monitoring services. A link to the form breach notification letters that Horizon Behavioral Health filed with the Attorney General of the Commonwealth of Massachusetts is below.