Ghost in the Router: China-Nexus Espionage Actor UNC3886 Targets Juniper Routers

Written by: Lukasz Lamparski, Punsaen Boonyakarn, Shawn Chew, Frank Tse, Jakub Jozwiak, Mathew Potaczek, Logeswaran Nadarajan, Nick Harbour, Mustafa Nasser

Introduction

In mid 2024, Mandiant discovered threat actors deployed custom backdoors on Juniper Networks’ Junos OS routers. Mandiant attributed these backdoors to the China-nexus espionage group, UNC3886. Mandiant uncovered several TINYSHELL based backdoors operating on Juniper Networks’ Junos OS routers. The backdoors had varying custom capabilities, including active and passive backdoor functions, as well as an embedded script that disables logging mechanisms on the target device.

Mandiant worked with Juniper Networks to investigate this activity and observed that the affected Juniper MX routers were running end-of-life hardware and software. Mandiant recommends that organizations upgrade their Juniper devices to the latest images released by Juniper Networks, which includes mitigations and updated signatures for the Juniper Malware Removal Tool (JMRT). Organizations should run the JMRT Quick Scan and Integrity Check after the upgrade.

Mandiant has reported on similar custom malware ecosystems in 2022 and 2023 that UNC3886 deployed on virtualization technologies and network edge devices