University of Hawaiʻi Cancer Center Ransomware Breach Exposes Data of Up to 1.2 Million People
The University of Hawaiʻi confirmed that a ransomware attack against the UH Cancer Center’s Epidemiology Division led to the theft of sensitive data affecting up to ~1.2 million individuals. The intrusion occurred in August 2025, and the university began issuing notifications in late February, including letters to 87,493 participants in the Multiethnic Cohort (MEC) Study and additional outreach tied to roughly 900,000 discovered email addresses. UH stated the incident did not impact Cancer Center clinical trials operations, patient care, other Cancer Center divisions, or UH student records.
Disclosed exposed data includes research and registry-related files containing names and Social Security numbers, and in some cases driver’s license numbers and health information associated with the MEC Study (1993–1996) and other diet/cancer studies, as well as historical datasets sourced from state transportation and voter registration records (late 1990s/2000s). Reporting also indicates the affected records include SSN identifiers from historical driver’s license and voter registration data, expanding the potential impacted population beyond the MEC cohort to approximately 1.15 million additional individuals whose information may have been present in those datasets.
Timeline
Mar 3, 2026
UH publicly discloses the ransomware breach and scope of impact
By 2026-03-03, the University of Hawaiʻi Cancer Center publicly confirmed that the August 2025 ransomware attack exposed sensitive data for nearly 1.2 million people. The disclosure clarified the affected division, the types of data exposed, and that the incident was confined to research operations.
Feb 23, 2026
UH begins mailing breach notifications to affected individuals
On 2026-02-23, the university began sending notification letters to more than 87,000 participants in the Multiethnic Cohort Study and started notifying other potentially impacted individuals. UH also offered 12 months of credit monitoring and identity theft protection to eligible victims.
Feb 23, 2026
Investigation finds legacy research data exposure affecting about 1.2 million
The investigation determined that compromised files included historical research and recruitment records dating back to the 1990s, exposing names, Social Security numbers, driver's license information, voter registration records, and some health-related data. UH said the breach affected approximately 1.2 million individuals, including Multiethnic Cohort Study participants and people tied to roughly 900,000 discovered email addresses.
Aug 31, 2025
UH engages attackers for decryptor and seeks destruction of stolen data
During response efforts, UH communicated with the threat actors to obtain a decryption tool and sought assurances that exfiltrated data would be securely destroyed. Multiple reports indicate the university acknowledged paying the attackers as part of this process.
Aug 31, 2025
UH disconnects systems, starts investigation, and notifies law enforcement
After identifying the attack, UH disconnected affected systems, removed the threat actor, notified law enforcement, and brought in external cybersecurity experts to investigate. Extensive encryption of affected data delayed restoration and the full impact assessment.
Aug 31, 2025
UH Cancer Center ransomware attack begins in Epidemiology Division
Around 2025-08-31, threat actors breached and encrypted systems supporting the University of Hawaiʻi Cancer Center's Epidemiology Division research operations. The university said the incident was limited to research systems and did not affect clinical trials, patient care, other divisions, or student records.
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