Pierluigi Paganini
October 30, 2025
Japanese multinational advertising and public relations company Dentsu, one of the largest marketing agencies in the world, announced that its U.S.-based subsidiary Merkle suffered from a cyber attack that exposed staff and client data.
“We detected abnormal activity in part of the network of Merkle, a company that leads the CXM (Customer Experience Management) field for our group’s overseas business.” reads the security incident notice published by the company. “We immediately initiated incident response procedures, proactively shutting down certain systems, and quickly took measures to minimize the impact, and the system has now been restored.”
The company took certain systems offline to mitigate the attack as part of their incident response plan.
The firm is investigating the security breach with the help of external cybersecurity firm and notified relevant authorities in each impacted country.
Dentsu confirmed hackers stole files from Merkle, exposing supplier, client, and employee data, including personal, payroll, and National Insurance details. Affected individuals are being notified and offered free dark web monitoring.
“The investigation identified that certain files were taken from Merkle’s network. A review of those files determined that they contained information concerning current and former employees.” reads a statement issued by Dentsu. “Our investigation is ongoing; however, at present we anticipate that the files include bank and payroll details, salary, National Insurance number, and personal contact details.”
The company states that its network systems in Japan were not impacted; however, it is currently unable to estimate the financial impact on the business
Dentsu has approximately 67,667 employees as of December 31, 2024. In fiscal year 2024, the company reported consolidated revenues of ¥1.41 trillion (around €10.2 billion at current JPY/EUR exchange rates).
Merkle, Inc. is a U.S.-based marketing and customer experience agency that operates as a subsidiary of Dentsu Group. It specializes in data-driven, performance-based marketing, leveraging analytics, technology, and digital platforms to help clients optimize customer experiences and drive growth. The company has over 16,000 employees globally and estimated annual revenue is around US $1.5 billion.
It is unclear whether the company fell victim to a ransomware attack; at this time, no ransomware group has claimed responsibility for the attack on Merkle or Dentsu.
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