Massive Data Breach at Bouygues Telecom Exposes 6.4 Million French Customers

French telecommunications powerhouse Bouygues Telecom has disclosed a major cybersecurity incident affecting 6.4 million customers, exposing sensitive personal and financial information. The breach occurred on August 4, 2025, when attackers infiltrated "specific internal resources," according to company statements. With 14.5 million mobile subscribers and €56.8 billion in annual revenue, the provider represents critical national infrastructure, making this intrusion particularly alarming.

The Anatomy of the Attack

The company confirmed unauthorized access to databases containing:
- Contact details and civil status information
- Service contract specifics
- Business customer enterprise data
- International Bank Account Numbers (IBANs)

While Bouygues emphasized that passwords and credit card data remained secure, the exposure of IBANs creates significant fraud risks. The company attributed the attack to a "known cybercriminal group" and has since implemented additional security controls while collaborating with France's National Cybersecurity Agency (ANSSI) and data protection authority (CNIL). Perpetrators face potential penalties of five years imprisonment and €150,000 fines.

"The situation was resolved as quickly as possible by Bouygues Telecom's technical teams, and all necessary additional measures have been implemented," the company stated in its press release.

Cascading Threats to Telecom Infrastructure

This incident follows Orange's July 25 network breach disclosure—another French telecom leader investigating potential data theft. The pattern mirrors attacks against U.S. telecom providers recently attributed to Chinese cyber-espionage group Salt Typhoon, suggesting telecommunications infrastructure has become a high-priority target for both criminal and state-aligned actors.

Security analysts note telecom providers present attractive attack surfaces due to their vast customer databases, interconnected systems, and role as connectivity gatekeepers. The Bouygues breach demonstrates how a single intrusion can expose millions—nearly half their mobile subscriber base—to cascading risks.

Mitigation and Customer Impact

Bouygues is notifying affected customers via SMS and email, warning of heightened phishing risks. The company specifically cautioned against sharing credentials with callers referencing personal account details—a common social engineering tactic following data breaches. While IBANs alone can't initiate transfers, customers should monitor accounts for suspicious activity.

This breach underscores the fragile balance between data collection and stewardship. As telecommunications providers amass increasingly detailed customer profiles, their security postures must evolve beyond perimeter defense. With France's CNIL now involved, regulatory repercussions seem inevitable—potentially accelerating industry-wide security reforms across Europe's critical communications infrastructure.

Source: BleepingComputer (Original reporting by Bill Toulas)