Gordejeva, JelizavetaMayer, AndreasPobiruchin, MonikaWendzel, SteffenWressnegger, ChristianHartmann, LauraFreiling, FelixArmknecht, FrederikReinfelder, Lena2024-04-192024-04-192024978-3-88579-739-5https://dl.gi.de/handle/20.500.12116/43973Running has become one of the most popular workout activities in the past years. Runners track themselves during training and big events like marathons races with dedicated wearable devices or smartphones. We analyzed freely accessible and supposedly anonymous respectively pseudonymous tracking data of three marathon events. Tracking data were collected by a single live GPS tracking provider, here Racemap. All data were publicly available. Thereby, we found out that it is possible to link these data sources with other public online resources to re-identify a person and to gather further sensible personal information (e.g., private or working addresses). Furthermore, we propose measures that participants, providers and organizers could carry out in order to ensure data privacy.enself-trackingdata privacyGDPRwearablesText/Conference Paper10.18420/sicherheit2024_0091617-5468