Incident Score: Analysis & Impact (CIRERN1784299363)
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Rankiteo Score Impact Analysis
Key Highlights From The Incident Analysis
- Timeline of EY's Breach and lateral movement inside company's environment.
- Overview of affected data sets, including SSNs and PHI, and why they materially increase incident severity.
- How Rankiteo’s incident engine converts technical details into a normalized incident score.
- How this cyber incident impacts EY Rankiteo cyber scoring and cyber rating.
- Rankiteo’s MITRE ATT&CK correlation analysis for this incident, with associated confidence level.
Full Incident Analysis Transcript
In this Rankiteo incident briefing, we review the EY breach identified under incident ID CIRERN1784299363.
The analysis begins with a detailed overview of EY's information like the linkedin page: https://www.linkedin.com/company/ernstandyoung, the number of followers: 11703543, the industry type: Professional Services and the number of employees: 407870 employees
After the initial compromise, the video explains how Rankiteo's incident engine converts technical details into a normalized incident score. The incident score before the incident was 775 and after the incident was 736 with a difference of -39 which is could be a good indicator of the severity and impact of the incident.
In the next step of the video, we will analyze in more details the incident and the impact it had on EY and their customers.
On 13 July 2026, Ernst & Young (EY) disclosed Data Breach issues under the banner "EY Data Breach After Third-Party Platform Compromise".
Ernst & Young (EY) notified affected individuals following a data breach involving a third-party IT service management platform used by its tax practice.
The disruption is felt across the environment, affecting Third-party IT service management platform (tax practice support tickets), and exposing Personal and financial information.
In response, teams activated the incident response plan, moved swiftly to contain the threat with measures like Affected systems secured, and stakeholders are being briefed through Notification letters to affected individuals.
The case underscores how Ongoing, with advisories going out to stakeholders covering 24 months of complimentary Experian IdentityWorks credit monitoring and identity restoration services (enrollment by October 31, 2026).
Finally, we try to match the incident with the MITRE ATT&CK framework to see if there is any correlation between the incident and the MITRE ATT&CK framework.
The MITRE ATT&CK framework is a knowledge base of techniques and sub-techniques that are used to describe the tactics and procedures of cyber adversaries. It is a powerful tool for understanding the threat landscape and for developing effective defense strategies.
MITRE ATT&CK® Correlation Analysis
Rankiteo's analysis has identified several MITRE ATT&CK tactics and techniques associated with this incident, each with varying levels of confidence based on available evidence. Under the Initial Access tactic, the analysis identified Supply Chain Compromise (T1195) with high confidence (90%), with evidence including third-party IT service management platform compromise, and supply chain such as true and Trusted Relationship (T1199) with moderate to high confidence (80%), supported by evidence indicating third-party platform used by EYs tax practice was compromised. Under the Credential Access tactic, the analysis identified Steal Application Access Token (T1528) with moderate to high confidence (70%), supported by evidence indicating unauthorized access to third-party platform between March 28 and April 12, 2026. Under the Collection tactic, the analysis identified Data from Local System (T1005) with moderate to high confidence (80%), supported by evidence indicating attackers downloaded client-related documents containing personal/financial data and Data from Information Repositories (T1213) with high confidence (90%), supported by evidence indicating compromised platform used to manage support tickets for tax-related engagements. Under the Exfiltration tactic, the analysis identified Exfiltration Over C2 Channel (T1041) with moderate to high confidence (80%), with evidence including data exfiltration such as true, and attackers downloaded client-related documents. Under the Impact tactic, the analysis identified Data Destruction (T1485) with lower confidence (30%), supported by evidence indicating no evidence of data misuse reported to date and Data Manipulation: Stored Data Manipulation (T1565.001) with lower confidence (40%), supported by evidence indicating personal and financial information exposed in tax-related documents. These correlations help security teams understand the attack chain and develop appropriate defensive measures based on the observed tactics and techniques.
Sources & References
- EY Rankiteo Cyber Incident Details: https://www.rankiteo.com/company/ernstandyoung/incident/CIRERN1784299363
- EY CyberSecurity Rating page: https://www.rankiteo.com/company/ernstandyoung
- EY Rankiteo Cyber Incident Blog Article: https://blog.rankiteo.com/cirern1784299363-third-party-it-service-management-platform-ernst-young-breach-march-2026/
- EY CyberSecurity Score History: https://www.rankiteo.com/company/ernstandyoung/history
- EY CyberSecurity Incident Source: https://cyberinsider.com/ey-says-client-tax-data-exposed-in-third-party-it-software-breach/
- Rankiteo A.I CyberSecurity Rating methodology: https://www.rankiteo.com/Images/rankiteo_algo.pdf
- Rankiteo TPRM Scoring methodology: https://static.rankiteo.com/model/rankiteo_tprm_methodology.pdf