アクト・セン株式会社Data breach / unauthorized access incident
- Occurred on
- May 1, 2026
- Announced on
- June 15, 2026
- Severity
- BIncidents centered on names and contact details.
- Scale
- Unknown
- Main impact
- A server of the work management system was subject to unauthorized access, and encryption damage believed to be from ransomware has been confirmed. The disclosure concerns impacts on current and former employees of four companies; the number of affected individuals is not stated.
- Information involved
- Email addressUser / member IDPasswordIdentity verification dataPhone numberFull nameDate of birth
- Cause / key point
- Encryption damage believed to be from ransomware occurred as a result of unauthorized access.About Ransomware
- Industry
- Manufacturing
- Listing / capital
- Unlisted
- Last updated
- October 20, 2026
Is this incident worth paying attention to?
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Reviewed byYutaro SasaoFounder & CEO, MediaLeap Inc.
CEO of MediaLeap Inc. Working on both sides of web advertising and web media since 2013; founded the company in May 2025.
Review scope: cross-checking against primary sources (official and government announcements), verifying claims stay within the facts, and checking source attribution。Last reviewed:
Written by:Leak Watch editorial team (AI-assisted drafts verified against sources by the editorial team) · Reviewer profile · Request a correction
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Attack method classification: Ransomware(Encrypting data and demanding a ransom)
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