German law enforcement messenger surveillance

German law enforcement agencies, including the Zollkriminalamt (ZKA) and the Bundeskriminalamt (BKA), have integrated ‘account cloning’ into their investigative operations. This technique allows authorities to monitor encrypted messenger services such as WhatsApp, Signal, and Telegram by using official web or desktop clients to establish secondary access points to a target’s account. This method is often achieved by intercepting SMS verification codes or scanning QR codes from seized devices, serving as an alternative to expensive state Trojans.

The technique was tested by the Zollkriminalamt in late 2023 and became a permanent investigative tool in August 2025. On January 20, 2026, the Federal Court of Justice (BGH) ruled that this practice constitutes ‘source telecommunications surveillance’ (Quellen-TKÜ). Under this legal classification, authorities are permitted to monitor real-time communication but are strictly prohibited from accessing historical chat logs.

The use of these methods has created a contradiction in security guidance, as agencies like the Federal Office for Information Security (BSI) and the Federal Office for the Protection of the Constitution (BfV) warn citizens against unauthorized device linking and phishing, even as law enforcement employs similar tactics.