German law enforcement agencies have reportedly found a way to monitor encrypted messages without breaking the encryption itself. The technique, known as messenger monitoring, uses standard linked-device features available in WhatsApp, Signal and Telegram.
Once authorities connect a police-controlled computer to a target’s account, the messaging service can deliver conversations directly to that device. However, German courts and privacy advocates have raised questions about whether the practice has a sufficient legal basis.
Police Use Features Built Into Messaging Apps
Documents published by German digital rights outlet Netzpolitik show that the country’s Customs Office started testing the method in late 2023. Officials reportedly warned that details should receive highly sensitive treatment to protect its effectiveness.
The method relies on functions designed to let users access their accounts from several devices. WhatsApp Web and Signal Desktop, for example, can connect a messaging account to a laptop or desktop computer.
German authorities can use the same functionality to link an account to a police-controlled device. Messages then arrive on that computer in decrypted form because the messaging service treats it as an authorised endpoint.
Therefore, investigators do not need to break end-to-end encryption or install spyware that controls the entire phone.
Authorities Need Access or Verification Codes
Police must first gain enough access to link the additional device. According to Netzpolitik, investigators can do this by physically accessing the target’s phone.
Authorities may also obtain verification codes through state-approved phishing or intercept SMS messages during authorised telephone surveillance. These codes allow them to add their own computer as a linked device.
Signal reportedly presents an additional concern. German security authorities warn that a successfully connected device may gain access to messages from the previous 45 days.
Telegram Suspect Discovered the Connection
Netzpolitik highlighted a 2022 investigation involving a suspected drug dealer in Lower Saxony. Police secretly linked a device to the suspect’s Telegram account.
The suspect noticed the unauthorised connection several hours later. However, officers had already copied the account’s message archive by that point.
Official documents indicate that German authorities made messenger monitoring a formal investigative practice in August 2025. Officials credited the technique with producing significant results in cases involving serious and organised crime.
Nevertheless, questions remain about how widely agencies use the method and which people they choose to monitor.
Police Linked Accounts Belonging to Witnesses
A 2020 case illustrates how authorities also used the technique against people who were not criminal suspects. A married couple voluntarily gave their phones to German police while officers questioned them as witnesses in an investigation involving their daughter.
The couple allowed investigators to inspect and photograph messages that their daughter had sent. While officers possessed the devices, they secretly activated WhatsApp Web and linked both accounts to a computer controlled by Germany’s Federal Criminal Police Office.
After returning the phones, investigators could potentially read new messages, view synchronised conversations and access WhatsApp contacts. The linked accounts could also allow police to send messages while appearing to act as the couple.
However, this access remained limited to WhatsApp. It did not let investigators monitor voice calls or use the phones’ cameras and microphones. Officers also could not read standard SMS messages or access unrelated applications through the linked connection.
German Courts Question the Legal Basis
The surveillance method has faced scrutiny within Germany’s legal system. In January 2026, the Federal Court of Justice ruled that secretly connecting to Telegram conversations amounted to surveillance.
That decision rejected an earlier legal interpretation that customs investigators reportedly continued to reference the following month. The ruling could affect how authorities justify similar monitoring operations in future cases.
The technology itself does not defeat the encryption protecting messages while they travel between devices. Instead, police add another authorised endpoint and receive the content after the messaging service decrypts it.
Consequently, strong encryption alone cannot prevent this type of access. Users must also monitor the devices linked to their accounts and remove any connection they do not recognise.
Encrypted Apps Face Broader Surveillance Pressure
German authorities are not alone in seeking alternative ways to monitor communications protected by end-to-end encryption. Law enforcement agencies in other countries have reportedly collected information from push notifications on iOS and Android devices.
Such techniques target data before encryption begins or after a device decrypts it. This approach allows investigators to avoid attacking the underlying cryptography while still accessing useful information.
The growing use of messenger monitoring highlights a wider privacy problem. Encrypted messages can remain mathematically secure, yet account features, connected devices and notification systems may still provide other routes to their contents.
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