kuronekoyamato.co.jp Domain Breach Exposure Report

The telemetry indicates a significant exposure event impacting kuronekoyamato.co.jp, with a total of 107,454 events recorded over the period from July 2025 to June 2026. The majority of these events, 83.4%, are classified as historical data breaches, totaling 89,646 incidents. Additionally, 16.6% of events, or 17,808 incidents, are identified as active infostealer logs. The timeline shows a notable increase in client-related events starting in August 2025 and peaking in March 2026, with employee-related events also showing sporadic spikes throughout the period. The primary sources of data leakage are identified as "Combolist sources" (99.9%), suggesting credential stuffing or account takeover attempts, and "Database dumps" (0.1%). Malware families associated with these events include LummaC2, Rhadamanthys, and Redline, all commonly used for credential harvesting and data exfiltration. Targeted services primarily include authentication and customer portal login endpoints, such as auth.kms.kuronekoyamato.co.jp and cmypage.kuronekoyamato.co.jp, indicating a focus on compromising user accounts and potentially sensitive customer information. The geographical breakdown shows a strong concentration of events originating from Japan, with smaller numbers from Vietnam, the United States, and Indonesia. Given the high volume of historical data breaches and active infostealer logs, coupled with the targeting of authentication services and the prevalence of credential-harvesting malware, this incident poses a critical risk to the organization and its customers. The reliance on "Combolist sources" suggests that compromised credentials are a primary vector, potentially leading to unauthorized access and further data exfiltration. Remediation efforts should focus on immediate credential rotation for affected users, enhanced monitoring of authentication endpoints for suspicious login activity, and a thorough review of data access controls. Furthermore, implementing robust endpoint security measures to detect and prevent infostealer malware and strengthening defenses against credential stuffing attacks are crucial next steps.