Dutch national police have deemed it “very likely” that a state-sponsored threat actor was behind a large-scale data breach discovered last week.

During the attack, unidentified hackers stole “work-related contact details,” including names, email addresses, phone numbers and private information from some of the agency’s 65,000 officers. 

In a statement released earlier this week, the police said local intelligence services had informed them that “another country or perpetrators acting on behalf of another country” could be responsible for the attack.

Few details have been revealed about the incident and its impact. 

“In order not to make the perpetrators any wiser and not to harm the investigation, no further information can be shared at this time,” the police said, adding that they have “implemented strong security measures” in response to the breach.

“Police officers are working day and night to prevent or counter new cyber threats and to track down the perpetrators.”

Dutch Justice Minister David van Weel said last week that the attack did not compromise the police’s “private data and research data.” He did not specify how the breach could affect officers working undercover.

A police spokesperson told local media that the attack caused “great concern” among employees, who were left wondering what specific data was involved and whether more information had been stolen.

The Dutch Police Union called the attack a "nightmare," emphasizing that the need for strong data protection within the police force has become painfully clear.

While the investigation into the incident is ongoing, the police have advised their employees to be cautious about suspicious apps, potential phishing emails, and issues with logging into their devices.