Clalit Health Services and the National Cyber Directorate on Wednesday said that they were investigating claims by the Iranian hacker group "Handala" regarding a large-scale breach of the organization's systems.
The group published patients' medical and personal documents as "proof" of their capabilities.
The "Handala" group, associated with Iran, released a combative statement under the title "Operation Justice for the Oppressed."
The hackers claim they gained access to Clalit's vast computer network, which includes hundreds of clinics and hospitals. The group published samples containing medical details of about 10,000 patients.
Among the documents distributed: test referrals, medical histories, Form 17s (claims commitments), and maternity leave requests.
The group presents the operation as part of a "cyber resistance" and a blow to Israel's healthcare infrastructure.
Clalit stated: "Following an announcement about a cybersecurity incident, we are examining the credibility of the message with the help of the organization's cybersecurity and information security teams."