DSL routers by ASUS and DIGICOM, Observa Telecom, Philippine Long Distance Telephone (PLDT), and ZTE are vulnerable to hard-coded “XXXXairocon” credentials.
A remote attacker may utilize these credentials to gain administrator access to the device.
Enable firewall rules so the telnet service of the device is not accessible to untrusted sources. Enable firewall rules that block SNMP on the device.