Major Ad Giant Dentsu Hit by Data Breach Affecting Thousands of Employees

Dentsu reveals hackers breached Merkle's network, stealing sensitive data of employees and clients, impacting UK operations significantly.

By Content Team

Oct 29, 2025

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Japanese advertising giant Dentsu disclosed hackers breached its subsidiary Merkle's network, stealing files containing sensitive employee and client data. The attack affected Merkle, a customer experience company with over 16,000 employees across 80+ locations.

Stolen files include personal contact details, salary information, bank data, and National Insurance numbers of current and former UK employees. Clients and suppliers were also impacted. Dentsu shut down some systems after detecting unusual network activity and brought in cybersecurity experts.

The company is notifying affected individuals and offering free dark web monitoring. While Dentsu's Japan operations remain unaffected, the breach will have financial consequences.

Source: SecurityWeek

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