EDPB Report Reveals Critical Gaps in Data Anonymization Practices Across EU

The European Data Protection Board (EDPB) has published a comprehensive report detailing critical findings from its December 2025 stakeholder event on anonymization and pseudonymization practices. The event brought together regulators, technology experts, and privacy advocates to confront mounting evidence that many organizations fail to meet legal standards for truly anonymizing personal data under the EU's General Data Protection Regulation (GDPR).

Key Regulatory Concerns

According to the report, core confusion persists around GDPR's distinction between anonymization (Article 4(5)) and pseudonymization (Recital 26). True anonymization requires irreversible data transformation where individuals cannot be re-identified by any means, while pseudonymization merely replaces identifiers with artificial keys – leaving data still subject to GDPR protections. The EDPB emphasized that incorrectly labeling pseudonymized data as "anonymized" creates dangerous compliance gaps, especially when combined with modern re-identification techniques.

"Organizations are underestimating how easily supposedly anonymous datasets can be reverse-engineered using AI cross-referencing," stated EDPB Chair Andrea Jelinek in the report. "When location data, transaction histories, or device identifiers undergo superficial masking instead of proper anonymization, they become privacy time bombs."

Technical Implementation Challenges

The stakeholder discussions revealed widespread technical shortcomings:

• Algorithmic weaknesses: Many companies rely on outdated anonymization methods like basic masking or tokenization that fail against modern linkage attacks
• Context blindness: Organizations anonymize data in isolation without considering how external datasets could enable re-identification
• Scalability issues: GDPR-compliant anonymization techniques often struggle with large-scale datasets common in big data analytics

California's Consumer Privacy Act (CCPA) faces parallel challenges, with the report noting similar re-identification risks in U.S. datasets. Both regulations impose severe penalties for privacy breaches resulting from inadequate anonymization, including GDPR fines up to 4% of global revenue.

User Impact and Corporate Consequences

For individuals, flawed anonymization enables hidden profiling and discrimination. The report cites cases where:

• Health data anonymized through aggregation allowed re-identification of patients with rare conditions
• Mobility data sold as "anonymous" was combined with public records to track individuals' daily routines
• Streaming service viewing histories were de-anonymized to target political ads

Companies face dual risks: regulatory sanctions and loss of user trust. The EDPB highlighted recent enforcement actions including:

• A €10.2M fine against a retail chain for using easily reversible pseudonymization in customer analytics
• A €6M penalty against a health app for claiming GDPR exemption based on inadequate anonymization

Required Changes

The report outlines urgent measures:

1. Validation protocols: Organizations must implement mathematical proof of irreversibility using modern techniques like differential privacy
2. Third-party audits: Regular assessment of anonymization systems by accredited experts
3. Dynamic re-evaluation: Continuous testing against evolving re-identification methods
4. Purpose limitation: Strict controls on combining anonymized datasets with other information sources

The EDPB plans to release updated anonymization guidelines by Q2 2026, signaling tougher enforcement ahead. As Jelinek concluded: "Anonymization isn't a compliance checkbox but a mathematical guarantee. Organizations gambling with pseudonymization while calling it anonymity will face severe consequences."