Data Breach at French Tax Office May Affect 678,000, Stoking Crypto Holder Fears

France is investigating a major data breach at the tax authority in which data from hundreds of thousands of people may have been stolen. A hacker claims to hold information on around 678,000 people, including sensitive tax and personal data. That is problematic for every affected taxpayer, but for wealthy crypto holders the risk could go further. France is also dealing with a series of violent attacks in which crypto and extortion play a role.

Hacker gains access to French tax authority systems

The French Ministry of Economic Affairs confirms that an attacker gained unauthorised access to systems of the Direction générale des Finances publiques, better known as DGFiP, at the end of June.

According to the French authorities, the attacker abused someone else’s identity. This gave them access to systems containing information on both individuals and companies. The hacker was able to view and export data before the access was detected and shut down.

The case became more widely known later, after a hacker using the name ZeroBytes claimed responsibility. According to information shared by FrenchBreaches, the attacker had gained access to internal servers, after which a connection to the tax authority’s VPN was also possible.

Using an internal tool, targeted searches could then be carried out for individuals and companies.

The hacker claims to have stolen data on around 678,000 people. This would include names, email addresses, tax identification numbers, information on family situation and tax data.

The French tax authority has not yet confirmed whether this number is correct. Nor have the full contents and authenticity of the database on offer been independently established. According to the information provided, the database is now being offered for sale on the dark web.

Wealthy crypto holders face extra risk

A particularly sensitive part of the claim is that the database, according to the hacker, contains data on 386 people who report an income of more than €1 million.

That does not automatically mean these people own crypto. Nor has it been confirmed that the stolen tax data specifically contains information about crypto holdings. Even so, the potential combination of identity, financial details and other personal data is worrying.

Criminals can combine different leaked databases. When one source shows that someone is wealthy and another reveals that the same person is active in crypto, a much more detailed target profile emerges.

That risk is no longer purely theoretical in France. In 2026, according to the figures provided, around 30 violent incidents involving crypto have already been recorded, with roughly $30 million in assets believed to be involved.

A striking example also shows that even outdated address information can be dangerous. A family that moved into the former home of a crypto millionaire was reportedly robbed three times. The current residents were not themselves the original target, but came into view because of their address.

France faces a series of major data breaches

The tax authority incident does not stand alone. Several French government services are facing cyberattacks and data breaches in 2026.

In April, hackers targeted the website of the Agence nationale des titres sécurisés, the agency that processes applications for passports, identity cards, residence permits and driving licences, among other things.