Employee data from advertising giant Dentsu leaked in hacker attack

Dentsu, one of the largest advertising agencies on the planet, has had its UK employee data exposed via a data breach in its trading divisions. Thousands of people were likely exposed.

The “big six” agency announced its UK employees were exposed after "unusual activity” on servers in Merkle’s network. Merkle, a Dentsu-owned American data consultancy, had an unknown volume of files taken from its systems.

“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,” Dentsu’s breach notice explained.

“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,”

the company explained.

While the company did not disclose the number of affected individuals, its current UK staff exceeds 2,500. The company has been operating in the UK for several decades, which means tens of thousands of people could be qualified as “former employees.”

We have reached out to Dentsu for comment but the company could not share any more details than it did in the data breach notice.

Meanwhile, the Tokyo-headquartered company said the data breach likely exposed employee information such as:

• Payroll details
• Salaries
• National Insurance numbers
• Personal contact details

Malicious actors could utilize the following details for identity theft and targeted phishing scams. Armed with salary data, determined attackers could attempt to target high earners to maximize profit-per-attack ratio.

Interestingly, Dentsu’s breach notice said the company “has taken measures to prevent the public disclosure of the data.”

That could mean many things, but since the attacks show traits of a ransomware campaign, Dentsu may have kept in contact with the attackers after the incident.

So far, no ransomware cartel has taken responsibility for the attack, which could mean the attack was of a different nature or the attackers’ ransom demands were met.

“Out of an abundance of caution, we are offering those whose information was potentially involved a one-year membership to a credit and dark-web monitoring service,” reads Dentsu’s breach notice.

The company said it has engaged a cybersecurity firm to assist with the ordeal. Law enforcement agencies, the UK's Information Commissioner’s Office (ICO), and the National Cyber Security Centre (NCSC) were also informed about the issue.

Dentsu UK is part of Dentsu, the Japanese advertising and public relations conglomerate. The company reported global revenue around $8 billion last year, with an estimated staff size of over 60,000.

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