Incident BriefingsDaiichi Kosho data at risk after NCG malware incident

Daiichi Kosho data at risk after NCG malware incident

The confirmed malware incident put outsourced-work data at risk; external leakage remained unconfirmed.

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Summary

  • Environment: One NCG employee computer holding outsourced-work data
  • Operational impact: Affected computer isolated; no Daiichi system impact confirmed
  • Financial impact: No incident cost established in the reviewed evidence
  • Record status: Developing record. Reviewed October 13, 2026; updated as evidence emerges.

What happened

Daiichi Kosho disclosed malware on a computer at Nippon Columbia Group. The computer temporarily held personal data for outsourced work. Its Japanese notice says external leakage remained unconfirmed. [2]

Impact

Approximately 8,724,000 records were potentially involved: 8,631,000 customer records after removing overlap and 93,000 employee records. This is a data-at-risk estimate, not confirmed theft or a unique-person count. Fields included names, sex, birth dates, email addresses and phone numbers; passwords were excluded. [2]

Timeline

  1. Computer isolated

    NCG isolated the affected endpoint.

    [2]

  2. Daiichi Kosho informed

    Daiichi Kosho received NCG’s report.

    [2]

  3. Inquiry desk opened

    A follow-up notice announced a dedicated freephone line.

    [1]

  4. Briefing updated

    This briefing was last reviewed and updated on October 13, 2026.

Threat Group & Attack Vector

Malware was identified on October 1–2. The disclosure does not establish its entry method or family. [2]

Actors

  • No threat actor group has been identified in the reviewed public evidence.

TTPs

  • No specific MITRE ATT&CK technique is currently mapped for this case.

Response

NCG reset credentials and commissioned forensic work. Daiichi Kosho said it would review vendor controls. [2]