Chinese-Made Zbtlink Routers Ship With Backdoor That Opens Unauthenticated Root Shells
Cybersecurity researchers have disclosed details of a "factory-shipped backdoor" implanted in at least 20 Chinese router models from Zbtlink. According to a new report from VulnCheck, the implant appears in all 21 firmware images currently available from Zbtlink that span more than 2 years. The backdoors are designed such that they start automatically and attempt to beacon to Chinese command-and-control (C2) infrastructure as often as every 35 seconds. They masquerade as a Linux kernel thread, but are actually userland processes running with root privileges while blending their true functionality with other legitimate kworker processes. The "phone home" implants have been codenamed ENDLESSDOORS . "ENDLESSDOORS, at its core, is a small tool called rctl (remote control linux)," Jacob Baines, VulnCheck Chief Technology Officer, said. "Uploaded to GitHub on January 14, 2015 and never touched again, this obscure repository implements a simple co...
î ‚Aug 06, 2026