Advertising tracking: German investigators bought mobile phone data

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Two German state criminal investigation offices have admitted to purchasing location data of third parties from data brokers and using it for investigations. The data was likely collected on smartphones for advertising purposes and aggregated by data brokers. There is no clear legal basis for the use of such data by investigative authorities.

The promise of modern smartphones is convenience: the weather app shows the rain radar, the navigation app guides you through traffic jams, the mobile game passes the time. What most users carelessly click away in everyday life is the associated consent to share their location. This data flows through convoluted paths of the advertising industry to data brokers, who use it to create precise movement profiles.

Data purchased for investigations

Research by Bayerischer Rundfunk (BR) and by Netzpolitik has revealed that at least two state criminal investigation offices (LKAs) in Germany have already specifically purchased data from commercial data brokers and evaluated it for their own investigations.

The LKA Mecklenburg-Vorpommern confirmed upon inquiry that they had used advertising-based location data to a small extent to analyze interconnections and involvement in online offenses and economic crime. Further purchases are not planned. The Brandenburg LKA also admitted to using data broker services "on a case-by-case basis." However, it left open whether this explicitly involved location data and whether it originated from the advertising industry.

Circumventing judicial authorization

The revelations burden official information management, as the legal basis for such practices is disputed by experts. If the police want to use conventional location methods such as cell tower triangulation, the legislature has set high hurdles for good reason: such an intrusion into privacy usually requires a court order.

With the largely unregulated purchase through private data brokers, this judicial authorization is de facto circumvented. The state data protection officer of Mecklenburg-Vorpommern, Sebastian Schmidt, has initiated an audit procedure against the LKA there as a result of the research. He sees a danger that strict protective rights are being circumvented through commercial data purchases.

Illegal misuse of purpose?

Criticism of the practice is forming among legal professionals. Munich criminal lawyer Mark Zöller classifies the use of this data by the state criminal investigation offices as unlawful. The data was never generated for the purposes of threat prevention or criminal prosecution. The police use therefore constitutes an illegal change of purpose that violates the fundamental right to informational self-determination. There is no legal basis for such action in the security laws.

The extent of data trading within German security authorities remains in the dark, as there is no transparency. A nationwide survey of all 16 state criminal investigation offices reveals a wall of silence. While five federal states denied its use, nine LKAs – including Bavaria, Berlin, North Rhine-Westphalia, and Saarland – refused any information, citing "secrecy reasons" or "police tactical concerns."

The federal government also remains silent on the issue: a parliamentary inquiry by the Left Party regarding potential data purchases by the Federal Criminal Police Office or the Federal Intelligence Service was not answered at the end of 2025 for reasons of state welfare, not even under exclusion of the public. Meanwhile, an expert opinion from the parliamentary scientific services concluded in November that the official purchase of data broker profiles is no longer an exceptional phenomenon.

National Security Issues

The problem extends far beyond individual data protection and touches upon issues of national security. So-called ADINT companies (Advertising-based Intelligence) offer specialized software solutions that make advertising data usable via graphical interfaces, such as a search field for movement profiles. International research shows that billions of locations worldwide can be analyzed through free data samples from these brokers. This affects not only criminals but millions of law-abiding citizens.

Since the profiles reveal the most intimate details, such as visits to clinics or even the movements of EU officials and members of the military, politicians from all parties are warning of blackmail and espionage by foreign intelligence services. German authorities are feeding this controversial market with taxpayer money.

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