netidee Scholarships: Active Measurements in Cellular Networks

Gabriel Gegenhuber investigated the security of cellular networks using active measurements in live operations and discovered security vulnerabilities in messaging services

Cellular networks are the backbone of global communication, but their increasing complexity—driven by technologies such as VoIP, eSIMs, VoWiFi, and commercial mechanisms like roaming and virtual operators—makes independent analysis increasingly difficult. At the same time, OTT messaging services such as WhatsApp and Signal have become central communication platforms, introducing new security and privacy challenges beyond traditional cellular networks.

This dissertation develops open-source, scalable measurement platforms that enable independent, reproducible studies of cellular networks, operator services, and OTT messaging applications without requiring operator cooperation. Using these tools, it uncovers security- and privacy-relevant weaknesses, including roaming billing inconsistencies, insecure VoWiFi deployments, and metadata leaks that enable user monitoring and denial-of-service attacks. The results demonstrate the value of active measurements for improving transparency and strengthening the security and privacy of modern mobile communication systems.

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