Introduction to the Threat of Tax Databases
A recent incident in France has highlighted the dangers of tax databases being used to compromise the security of cryptocurrency investors. A tax employee in Bobigny used internal software to compile dossiers on cryptocurrency specialists, billionaire Vincent Bolloré, prison guards, and a judge. She then passed this information on to criminals, who used it to attack a prison officer at his home in Montreuil. The employee was paid €800 for her services, which included providing the attackers with sensitive information about their targets.
Understanding the Threat Model
The threat model in this case is not based on sophisticated hacking, but rather on the extraction of data by insiders with legitimate permissions to secondary markets. This is a growing concern, as it allows attackers to gain access to sensitive information about individuals, including their addresses, phone numbers, and family structures. The French Police Inspectorate recorded 93 investigations for breach of professional secrecy and 76 for database diversion in 2024, highlighting the scale of the problem.
Insider Threats and Data Extraction
The economics of the attacker’s entity are such that it is highly profitable to sell access to sensitive information. Database queries are sold like mass-produced goods at transparent prices, with prices ranging from €30 for vehicle registration searches to €250 for decommissioning an illegal vehicle. The risk of detection is low, and the reward is high, making it an attractive option for insiders with legitimate access to tax, law enforcement, and judicial databases.
France’s Response to the Threat
In response to the growing threat, France has taken steps to protect the privacy of cryptocurrency investors. In August 2025, the government issued a decree deleting the private addresses of crypto directors from the RCS commercial register. This measure protects against physical aggression and harassment, with law enforcement, customs, and tax administration still having access. However, the proposed asset declarations for 2026 are causing new exposure, and the threat landscape is shifting from technical security to identity security.
Identity Security and Physical Coercion
Once attackers solve the identity problem, coercion is easy. The finality of crypto transfers shifts the threat landscape from technical security to identity security. France’s 2026 budget proposal includes a 1% annual tax on crypto holdings over €2 million, requiring self-custody and offshore holdings to be declared. This policy creates a honeypot: a government-maintained list of wealthy crypto holders, including their addresses. The technical community refers to cryptosecurity as key management, but the Bobigny case shows that key management is irrelevant once physical coercion is introduced into the threat model.
Conclusion and Recommendations
The Bobigny case highlights a regulatory paradox. European authorities are expanding crypto transparency through mandatory KYC, reporting to wallet providers, and DeFi transaction tracking to combat money laundering and tax evasion. However, these requirements create centralized databases that map identities to assets, making them valuable to attackers. To mitigate this risk, it is essential to implement robust security measures, including confidentiality of registration, tightened controls within government systems, and continued monitoring of insider-plus-access-for-sale incidents.
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