CommonSpirit Health, a large medical organisation located in Chicago, has revealed that more than 620,000 patients’ personal information was compromised in a ransomware assault in October.

On October 5, CommonSpirit Health, which runs more than 700 care locations and 142 hospitals throughout 21 states, said that there was a “IT security problem.” The corporation at the time refused to comment on the nature of the issue that prevented access to electronic health records and slowed down patient treatment in numerous locations, or to confirm or deny whether or not patient information or health data had been compromised.

A December update from CommonSpirit revealed that the issue was a ransomware assault. Threat actors breached the network of Franciscan Health, a 12-hospital affiliate of CommonSpirit Health, between September 16 and October 3, the organisation said, and “may have gained access to certain files, including files that contained personal information” of patients and family members of patients treated at the organisation.

While CommonSpirit’s inquiry is continuing, this information may contain personal details including names, residences, phone numbers, birth dates, and employee ID numbers. The business claims it has found no indication that any personal information has been abused as a consequence of the incident, and that the attackers did not get access to medical record numbers or insurance IDs.

The number of users whose information was compromised is unclear from the update. But the United States Department of Health data breach site – where healthcare businesses are legally compelled to disclose data breaches involving over 500 persons – confirms that threat actors obtained the personal data of 623,774 patients during the CommonSpirit ransomware assault.

CommonSpirit “rapidly moved to defend its networks, control the event, initiate an investigation, and guarantee continuity of care” after finding the ransomware assault, as the amended warning explains.

CommonSpirit has contacted the authorities and will assist them with their inquiry. After being patched and secured, systems were reintegrated into the network with heightened network and system-wide monitoring.

CommonSpirit representative Chad Burns did not immediately react to our request for comment, and the firm has not yet identified the ransomware organisation responsible for the assault.

TechCrunch has researched the dark leak websites of numerous prominent ransomware gangs, but thus yet, no one has claimed credit for the assault.

According to Brett Callow, a security analyst at Emsisoft, ransomware has affected at least 15 U.S. health systems in 2022, with those systems responsible for 61 hospitals throughout the nation. Personal information, including medical records, was compromised in at least 12 of these occurrences.