This write up discusses how to leave a persistent root shell on a Telstra 4GX portable router.
You can download it from the following link: https://packetstormsecurity.com/files/download/140674/telstra4gx-exec.txt
Source: https://packetstormsecurity.com/files/140674/Telstra-4Gx-Portable-Router-Persistent-Root-Shell.html