Your data will be auctioned off immediately
According to research by hacker Mick Beer, several popular Dutch apps send data to advertising auctions, also known as real-time bidding. Data such as an advertising ID, location information, language settings and network data can be used to sell advertising space to interested parties.
The researcher looked at apps including Buienalarm, Marktplaats, 9292 and Voetbal International (VI). It was found that these apps utilise advertising networks and data collection in various ways.
A striking finding came from Marktplaats. During a test, approximately 85 per cent of data usage whilst using the app was attributed to advertising and tracking traffic. According to the measurements, the actual content you are searching for – such as products and adverts – accounted for only a small proportion of the total data traffic.
At the other end of the scale is 9292. That app was found to generate far less advertising traffic. In the measurements, around 1 per cent of data usage was attributed to adverts and tracking. Nevertheless, the research also revealed that the app was found in leaked data broker files. According to the researcher, this shows that an app can be relatively economical with advertising traffic, whilst data can still end up with data brokers via advertising networks.
Weather apps were also scrutinised. The research revealed that, in the case of Buienalarm, device data is sent directly to advertising auctions. A similar process is said to take place for Buienradar, but via Google’s servers, making it less visible on the device itself.
Voetbal International stood out because, according to the measurements, the app was found to share an advertising ID directly with a company that builds advertising profiles. In addition, the app uses various advertising and measurement platforms.
The researcher emphasises that these are snapshots from June 2026 and that apps and advertising systems are constantly changing. Furthermore, not all findings have been fully confirmed on physical devices; some analyses were carried out in a controlled test environment.
Nothing will change immediately for users, but the research does highlight just how significant a role advertising technology can play behind popular apps. Even with apps you use every day for the weather, travel or online shopping, an extensive network of advertising and data services is often at work in the background.
Via Mick Beer
