[News](/news) Medibank Data Breach Impacts 9.7 Million Customers [Blog](/blog)[Breaches](/breaches)[Resources](/resources)[News](/news) # Medibank Data Breach Impacts 9.7 Million Customers ##### [Edward Kost](/team/edward-kost) November 11, 2022 Medibank suffered a data breach that compromised 9.7 million current and former customers - an impact with a chilling resemblance to the Optus data breach that occurred [less than a month earlier](https://www.upguard.com/news/optus-data-breach-exposes-up-to-9-8-million-customers-details). The attack vector that facilitated the breach was a set of stolen high-ranking corporate credentials that were sold on a cybercriminal marketplace. Cybercriminals believed to be affiliated with the defunct ransomware gang, REvil, used these credentials to log into Medibank's network and exfiltrate the customer database.  Upon detecting unusual activity within its network, Medibank’s security team promptly located and shut down two backdoors facilitating data transfer during the attack. This likely caused an unexpected disruption to the attack, preventing the cybercriminals from encrypting Medibank's systems - the characteristic final stage of a ransomware attack. Unfortunately, the attack wasn't disrupted before 200 GB of customer data was stolen. The cyber criminals demanded a ransom payment of US$10 million to prevent the stolen database from being published on the dark web (a cybercriminal network accessible through a specialised Tor browser). Medibank denied a ransom payment. In an effort to reverse this decision and extort payment, the cybercriminals have published segments of sensitive customer data on the dark web, promising to publish more if the ransom payment isn't made. This story is still unfolding. *Is your organization at risk of a data breach? *[*Click here to find out >\ ‍*](https://www.upguard.com/instant-security-score) #### Keep Learning about the Medibank Data Breach ‍ * [What Cause the Medibank Data Breach?](https://www.upguard.com/blog/what-caused-the-medibank-data-breach) * [The Medibank Data Breach (Complete Timeline of Events)](https://www.upguard.com/breaches/medibank-data-leak#toc-original-post) ## How secure is Medibank? Medibank provides private health insurance products in Australia, offering hospital cover, extras cover, and combined packages to individuals and families. The company also offers travel insurance, pet insurance, and specialized health cover for overseas visitors and students. * View our free preliminary report on Medibank’s security posture * 13 risk factors, including email security, SSL, DNS health, open ports and common vulnerabilities [View Medibank's score](/security-report/medibank) [View score](/security-report/medibank) [https://www.medibank.com.au/](/security-report/medibank) ### Sign up for our newsletter UpGuard's monthly newsletter cuts through the noise and brings you what matters most: our breaking research, in-depth analysis of emerging threats, and actionable strategic insights. ## Latest news Stay up-to-date with the latest news in cybersecurity. [](/news/hugging-face-data-breach-2026-07-20) #### [Hugging Face data breach: key facts and what we know so far](/news/hugging-face-data-breach-2026-07-20) A data breach involving Hugging Face was reported in July 2026. 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