Hauts-de-Seine Department Hit by Major Cyberattack, Systems Taken Offline as Precaution

On May 20, 2025, the Hauts-de-Seine department in France was hit by a large-scale cyberattack, forcing local authorities to shut down all IT systems and communication channels indefinitely.

The department council announced the cyberattack in a message on X (formerly Twitter):

"Le Département a été victime d’une cyberattaque de grande ampleur. L’ensemble des systèmes d’information et des moyens de communication habituels ont été désactivés pour une période indéterminée."

("The Department was the victim of a large-scale cyberattack. All information systems and usual communication channels have been deactivated for an indefinite period.")

According to La Tribune, the early-morning cyberattack rendered the entire IT infrastructure inoperable, including network access, applications, and internal communication systems.

As of now, the exact nature of the attack has not been disclosed. It remains unclear whether it involved ransomware, a DDoS attack, or another form of intrusion.

IT teams and service providers are fully mobilized to assess damage, protect sensitive data, and begin restoring access, and local authorities say that measures are being taken to protect agent and user data.

This incident is part of a growing wave of cyberattacks targeting public institutions, particularly local governments and critical infrastructure providers. In recent years, regional authorities across Europe and beyond have been increasingly targeted by threat actors looking to disrupt essential public services, exfiltrate personal and administrative data, and demand ransom payments in exchange for restoring access.

With 1.6 million citizens dependent on Hauts-de-Seine's services, long-term disruption could inflict severe damage, from stalled social support programs to delayed housing, education, or administrative functions.

The Risk to Citizen Data

Even though authorities have not confirmed a data breach, the shutdown of systems suggests that data exposure or compromise is a real concern. If attackers have accessed such data, it could lead to identity theft, phishing scams, and even geopolitical or corporate espionage.

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