Mass General Brigham Data Breach
Status: Confirmed
Breach Intelligence Summary
Entity: Mass General Brigham · Actor: Cl0p · Source: DataBreach.com / ObscureIQ intelligence
Attack: Ransomware via Network intrusion / ransomware deployment
Timeline: Breach (May, 2023) · Reported (Dec, 2024) · Leak (12/4/24)
Exposure: 4.1M+ records · Email, Phone Number, Name, Home Address, Medical Diagnosis
Status: Confirmed · Risk: High (Medical identity fraud + Phishing / SIM swap)
Summary
The Mass General Brigham Health Plan data breach linked to the exploitation of a vulnerability in Progress Software’s MOVEit Transfer platform by the Cl0p ransomware group exposed extensive patient information managed through Welltok’s systems. The breach compromised over 4 million records including sensitive personal and medical data such as full names home addresses phone numbers email addresses dates of birth and insurance provider details.
About Mass General Brigham
Mass General Brigham is the organization affected by this breach. User data may have been generated through account creation, service usage, or business operations.
If you have interacted with Mass General Brigham in any capacity, your data may be included in this breach.
Threat Actor: Cl0p
This breach has been attributed to Cl0p. The group is known for data theft campaigns targeting organizations through various intrusion methods.
- Network intrusion / ransomware deployment
Breach Exploitation Status
High
Status
Detected
Possible
Detected
Unknown
Unknown
3–5 years
Phone numbers and addresses change over time but remain valid long enough for sustained exploitation campaigns.
Data Points Exposed
Dark Web Verification
Status: Confirmed
- Dataset containing approximately 4.1M+ records has been identified in breach intelligence sources.
- The data is indexed and searchable across breach notification platforms.
Impact
This breach carries high risk due to the nature of exposed data fields and the scale of affected records.
- Targeted phishing referencing Mass General Brigham accounts or services
- Medical identity fraud and insurance scams
- SIM-swap attempts where phone numbers are present
- Physical mail scams and address-based identity verification fraud
- Data broker enrichment and resale
Recommendations for Impacted Individuals
If you believe your information may be included:
Non-clients may request a breach impact review.
Mass General Brigham account updates
Medical billing or insurance notices
Password reset requests
Verify directly through official channels.
Email compromise is often the first pivot point.
Frequently Asked Questions
In May, 2023, Mass General Brigham experienced a data breach that resulted in the exposure of approximately 4.1M+ records containing personal information.
The exposed data includes Email, Phone Number, Name, Home Address, Medical Diagnosis.
Approximately 4.1M+ records were affected based on current breach intelligence.
Yes. This breach is treated as confirmed based on data observed in breach intelligence platforms.
Data circulation has been detected across breach-sharing channels. Downstream exploitation risk exists based on the nature of the exposed fields.
Rotate passwords associated with Mass General Brigham, enable multi-factor authentication on email and financial accounts, and monitor for suspicious activity.
Protect Yourself
Check If You’re Affected
Enter your email to check if your data appears in this breach.
Get Free Breach Alerts
Be the first to know when new breaches are disclosed. Free forever.
High-Risk? Get an Exposure Audit
Executives, public figures, and high-net-worth individuals face elevated risk. Our team provides full-spectrum exposure audits and threat monitoring.
Corporate Accountability
Organizations that collect personal data have a duty to implement reasonable safeguards and to notify affected individuals when breaches occur.
Scope assessments may evolve as investigations continue. Users should not rely solely on early estimates when making risk decisions.
ObscureIQ Advisory
We combine proprietary dark web access with commercial and restricted breach intelligence to verify exposure and assess real-world risk.
- A public-facing individual
- A high-profile executive
- A customer of Mass General Brigham
- Or simply concerned about credential reuse
We can confirm whether your information is circulating and evaluate downstream threat vectors.