Japanese multinational advertising and public relations company Dentsu, one of the world’s largest marketing agencies, announced that its U.S.-based subsidiary Merkle had suffered a significant cyberattack. The security breach led to the exposure of both staff and client data. According to the company’s notice, they “detected abnormal activity” within Merkle’s network, which leads the Customer Experience Management (CXM) field for Dentsu’s overseas business. They immediately initiated incident response procedures, proactively shutting down specific systems to quickly minimize the impact, and the affected systems have since been restored.
The company’s swift action to take certain systems offline was a key part of their plan to mitigate the attack. Following the initial incident response, Dentsu launched a thorough investigation into the security breach. To ensure a comprehensive review, the firm enlisted the help of an external cybersecurity company and has notified all relevant authorities in each country that was impacted by the incident.
Dentsu confirmed that hackers successfully stole files from Merkle’s network. A review of these compromised files determined that they contained sensitive information concerning current and former employees. This exposed data includes personal contact details, as well as critical bank and payroll information, salary figures, and National Insurance numbers. The company is in the process of notifying all affected individuals and is providing them with free dark web monitoring services to help safeguard their identity.
The broader Dentsu organization stated that its network systems in Japan were not affected by the breach. However, the company, which reported consolidated revenues of approximately $10.2 billion in fiscal year 2024 and employs over 67,000 people, is currently unable to estimate the full financial impact this security incident will have on its business operations. Merkle itself is a large U.S.-based marketing and customer experience agency specializing in data-driven strategies, with over 16,000 employees globally and estimated annual revenue of around $1.5 billion.
While the investigation is ongoing, it remains unclear whether the company fell victim to a ransomware attack. At this time, no known ransomware group has publicly claimed responsibility for the attack on either Merkle or its parent company, Dentsu. The focus remains on completing the review of the compromised data and ensuring all affected parties are supported.
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