French prosecutors have opened an investigation into a sophisticated cyberattack on Crédit Mutuel Arkéa involving fraudulent transfers estimated at around €100 million, as the Brittany-based banking group races to recover the stolen funds.

Confirming the attack on Wednesday, Crédit Mutuel Arkéa said that hackers had targeted its own accounts rather than those of its customers, insisting that client savings and deposits were safe. The Paris prosecutor's office said it had opened an investigation on 4 November after receiving a complaint from the bank.

The investigation is being handled by France's specialist cybercrime police unit, OFAC, and focuses on suspected hacking by an organised criminal group.

While the full financial impact remains unclear, the attack represents a significant breach of a major French financial institution and raises fresh questions about the security of banking networks.

Data-rich systems and weak security: why France is a target for cyberattacks Cryptocurrency Crédit Mutuel Arkéa said the attackers had gained access to its systems through the platform of an external service provider, allowing them to initiate fraudulent transfers from the bank's own account to other financial institutions.

The money may subsequently have been converted into cryptocurrency through specialised trading platforms, potentially complicating efforts to trace and recover the funds.

The group stressed that its online banking subsidiary Fortuneo had not been used as an entry point and that no customer accounts had been accessed to carry out the transfers.

It also ruled out human error within the bank, describing the incident as a sophisticated external attack.

French regional newspaper and cryptocurrency news outlet CoinDesk reported that as much as €118 million had been diverted. The bank declined to confirm that figure but acknowledged that it reflected the approximate scale of the incident. It said some of the money had already been blocked, while efforts were continuing to recover the remainder.

"Our teams are continuing their work to precisely assess the financial consequences of this attack. It is still too early to give a final figure," a bank spokesperson said.

Investigators are now seeking to establish how the attackers gained access, who was responsible and where the stolen funds were transferred.

The attack has not been publicly claimed, and the bank has provided no information about the identity or possible motives of those responsible.

Warnings sent to French taxpayers after hackers allegedly sell stolen data Attack contained Crédit Mutuel Arkéa said its security systems had quickly detected suspicious activity, allowing it to contain the attack and temporarily suspend certain transfers. Almost all operations had resumed by Wednesday morning.

"This incident has had no impact on customer assets and has only caused a delay in the execution of certain transfers," the bank said, insisting that its financial stability was not at risk.

Headquartered near Brest, Crédit Mutuel Arkéa serves 5.8 million customers and manages more than €211 billion in assets. The group reported a net profit of €230 million in the first half of 2026.

The attack comes amid growing concern among European regulators over cyber threats to financial institutions, particularly as banks rely increasingly on interconnected systems and external service providers.

Advances in artificial intelligence have also raised fears of more sophisticated attacks, making cybercrime harder to detect and prevent.

The bank has urged customers to remain alert to phishing attempts exploiting publicity surrounding the incident. It has not confirmed whether any customer data was compromised.