Obfuscation detection using matrix complexity features of binary grayscale images

Sebastian Raubitzek, Sebastian Schrittwieser, Caroline König, Patrick Felbauer, Kevin Mallinger, Andreas Ekelhart, Edgar Weippl, Computers & Security, https://lnkd.in/gaYgBDWW.
Download at https://lnkd.in/dcfxBSa8

Nice interview with Aljosha on our current WhatsApp paper (University of Vienna and SBA Research): https://netzpolitik.org/2025/interview-zu-whatsapp-von-emojis-zum-mega-datenleck/

The full paper as preprint: https://arxiv.org/abs/2511.20252

Gabriel K. Gegenhuber, Philipp É. Frenzel, Maximilian Günther, Johanna Ullrich und Aljosha Judmayer: Hey there! You are using WhatsApp: Enumerating Three Billion Accounts for Security and Privacy. In Network and Distributed System Security Symposium (NDSS), 2026.

"“Well, scientists now know a lot of phone numbers,” the responsible parties might have thought, “So what?” Repeated warnings submitted ... filed away. Only when the researchers submitted a draft of their paper twice and its uncoordinated publication was imminent did Meta wake up: a surprising amount can be read from the data, and for some users, it can be life-threatening."

Heise: https://www.heise.de/en/news/3-5-Billion-Accounts-Complete-WhatsApp-Directory-Retrieved-and-Evaluated-11083244.html
FutureZone: https://futurezone.at/apps/whatsapp-sicherheitsluecke-alle-nutzer-betroffen-contact-discovery-anfragen/403104148