Universidad Carlos III de Madrid (UC3M), in collaboration with the National Cybersecurity Institute (INCIBE), an entity under the Ministry for Digital Transformation and Public Administration through the Secretariat of State for Telecommunications and Digital Infrastructure, have promoted the development of a new probabilistic metric designed to more accurately measure the level of privacy and protection that users have in different databases.

The research, recently published in the scientific journal Array, involved reviewing the metric commonly used in the field of data privacy (K-anonymity) before proposing a new system with the intention of improving it.

“K-anonymity has been used for years, but it only measures how many people are like you within a database, so it doesn't reflect whether a user is actually well protected or not,” explains Rubén Cuevas Rumín, deputy director of the UC3M–Banco Santander Joint Institute in Financial Big Data. “What our metric proposes is an alternative measure that incorporates probabilistic information rather than simply indicating how many users match others.”

This new method estimates the probability that one individual resembles another user based on the data set within the system (e.g., age, gender, interests, etc.), thus providing much more useful information for evaluating and comparing the privacy of its users.

“This approach allows us to examine in greater detail the level of anonymity offered by different digital platforms and understand how small changes in the way data is stored can have a major impact on privacy,” says Rubén Cuevas.

A metric tested through practical use cases

The researchers have applied this metric to platforms such as LinkedIn, X and Meta, and the results show significant differences between them. “We have seen that LinkedIn and X provide greater privacy protection than Meta. We have also found that, with very simple changes, such as replacing a user's exact age with an age range, Meta could improve its privacy level more than tenfold,” explains Rubén Cuevas.

The researchers emphasise the importance of users being aware of the level of privacy provided by the digital services they use in order to reduce the risks associated with leaks or misuse of personal information.

“People should be aware of which databases are storing their information and what protection they provide, as leaks can lead to dangerous practices if the systems are not well designed,” concludes Rubén Cuevas.

ANTICIPA Project

This project is part of the agreement between INCIBE and UC3M entitled ANTICIPA, included in the Strategic Projects in Spain, within the framework of the Recovery, Transformation, and Resilience Plan, with funding from the Next Generation-EU Funds. These initiatives are part of the Global Security Innovation Program, included in the Recovery, Transformation, and Resilience Plan (PRTR), through Component 15. Investment 7 Cybersecurity: Strengthening the capabilities of citizens, SMEs, and professionals and promoting the sector.

The National Cybersecurity Institute is an entity under the Ministry for Digital Transformation and Public Administration through the Secretariat of State for Telecommunications and Digital Infrastructure, consolidated as a benchmark entity for the development of cybersecurity and digital trust among citizens and businesses. It is also a driver of social transformation and an opportunity for innovation, promoting R&D&I and talent.

Carlos III University of Madrid (UC3M) is a Spanish public university that excels in research, teaching, and innovation. It ranks as the best Spanish public university in employability according to The Global University Employability Ranking and Survey 2026; among the top universities in Spain for its overall performance in the latest edition of the U-Ranking; and among the best universities in the world in the QS World University Rankings 2026. It is also the first university in Europe to achieve dual ACEEU accreditation for its contribution and impact on the industrial and social fabric. It also has other accreditations and quality distinctions, such as the EUR-ACE seal in the field of engineering and AACSB accreditation in business and finance programs.

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