Fraud Management & Cybercrime
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Incident & Breach Response
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Ransomware
Cybercrime Group First Listed Ohio Health System as a Data Theft Victim Last June

Ohio-based Kettering Health is notifying current and former patients that their personal, health and financial information was potentially compromised in a May 2025 ransomware attack and data theft incident claimed by cybercriminal gang Interlock.
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Interlock last June published at least some of the 941 gigabytes of data the gang claimed at the time to have stolen.
As of Tuesday, Interlock’s data leak site still listed the healthcare organization as a victim, with 950 gigabytes of Kettering Health data purportedly available, including 732,490 files and 20,251 folders (see: Ohio Health System Responding to Cyberattack, Fraud Scams).
The healthcare system last May warned patients of scam calls from fraudsters pretending to be medical bill collectors from the organization requesting credit card payments. Affiliated with the Seventh-day Adventist church, Kettering operates 14 medical centers and more than 120 outpatient facilities in Western Ohio, and has more than 1,800 physicians and 15,000 employees.
Kettering Health reported the data breach to federal regulators last July as a hacking incident involving a network server having affected 501 individuals, a placeholder estimate that it hasn’t yet updated.
Kettering Health on Tuesday declined Information Security Media Group’s request for additional details about the incident, including the total number of individuals affected.
In a breach statement posted on its website, Kettering Health said that on or about May 20, 2025, it became aware of suspicious activity affecting certain systems within its network.
An investigation determined unauthorized actors accessed Kettering Health’s environment between April 9, 2025, and May 20, 2025, and that certain files and folders within the network were potentially viewed and acquired. In a frequently asked questions about the incident, the health system confirmed the incident was carried out by the Interlock ransomware group.
Stolen information but includes names, Social Security numbers, financial account numbers, driver’s license numbers, medical and treatment information, health insurance information, billing and claim information, passport numbers, and usernames and associated passwords.
The cyber incident disrupted Kettering Health’s IT environment for several weeks, affecting patient care services, forcing the cancellation of elective inpatient and outpatient procedures. Kettering’s emergency rooms temporarily diverted patients to other medical facilities.
Kettering Health said it has worked with federal law enforcement agencies regarding the incidents. The organization said it is reviewing its policies and cybersecurity practices on an ongoing basis to help prevent falling victim to similar incidents in the future.
Kettering Health was among several healthcare sector entities listed as victims on Interlock’s darkweb site last spring and summer, prompting an alert from the Cybersecurity and Infrastructure Security Agency, the FBI, the U.S. Department of Health and Human Services and the Multi-State Information Sharing and Analysis Center (see: Feds Warn Health, Other Sectors of Interlock Threats).
Interlock, which exfiltrates data then encrypts victims’ systems with ransomware, targets organizations across North America and Europe. Besides medical providers, the gang’s long list of other victims includes schools, construction, manufacturing, real estate and law firms.
Ransomware monitoring website Ransomware.live as of Tuesday counted at least 96 Interlock victims since first appearing on the cybercrime scene around October 2024.
