The University Hospital Centre in Zagreb, Croatia, has suffered a significant data breach, with stolen data reportedly leaked on the LockBit ransomware group's dark leak site.

This incident occurred barely a week after the hospital was targeted by a cyberattack on 27 June, reported Cybernews.com.

Local media reports indicate that the publicly funded teaching hospital, also known as KBC Zagreb, resumed online operations within 24 hours of the attack, which was carried out by the Russian-affiliated cybergang. Restoring the hospital's IT systems required the expertise of over one hundred professionals.

Hospital officials have disclosed that the cyberattack had a severe impact on their networks, leading to emergency patients being redirected to other hospitals in Zagreb. According to Croatian Radio, the facility was described as having been taken "back 50 years—to paper and pencil". Despite the challenges, patient safety was reportedly not compromised.

"All tests can be done to some extent, but the radiological system, which is particularly dependent on information support, is perhaps the most severely affected," stated KBC Zagreb’s head of Emergency Admissions professor Ivan Gornik.

Established in 1942, the University Hospital Centre is recognised as Croatia's largest medical facility. It caters to approximately 10,000 citizens daily, operating across two main campuses and three additional locations in the city. The hospital boasts 30 clinics, seven specialised institutes, over 2,000 beds, and a workforce exceeding 7,500, which includes nearly 1,000 doctors. It is also home to one of Europe's few gamma knife treatment centres.

The report from Cybernews.com revealed that LockBit claims to have stolen a vast array of files, including "medical records, patient exams and studies; doctors' research papers; surgery, organ and donor data; organ and tissue banks; employee data, addresses, phone numbers, etc.; employee legal documents; data on donations and relationships with private companies; donation book; medication reserve data; personal data breach reports and much more".

The cybergang has also allegedly uploaded a sample of 12 documents as evidence of the attack.

While the hospital has not confirmed the specifics of the data leaked, it has engaged the appropriate authorities to initiate a criminal investigation to determine the full extent of the incident's impact.