You can configure MAC address filtering to prevent unauthorized network access on Huawei ONT:
https://support.huawei.com/enterprise/en/doc/EDOC1100009117/dbc30c13/how-to-configure-mac-address-filtering-to-prevent-unauthorized-network-access-on-huawei-ont-hg8240-hg8240t-hg8240w-hg8245-hg8247-hg8247h
In addition, you can do the following safety measures:
1. Please use the internet stealing software with caution, such as a Wi-Fi master key. The stealing software will share its wireless / Wi-Fi network information to the server without the user ’s knowledge. The stealer searches for the wireless / Wi-Fi network name and obtains the wireless / Wi-Fi network from the server through the 3G or 4G network Key, causing the wireless / Wi-Fi network to be "stolen".
2. Confirm whether you have encrypted the wireless / Wi-Fi network. Log in to the ONT WEB interface (refer to how to log in to the ONT WEB interface). Select "Network> WLAN Configuration-Wireless / Wi-Fi Basic Configuration" page, and set a password at "Wireless / Wi-Fi Network Key".
3. The wireless / Wi-Fi password is too simple to be cracked. Select "Authentication Mode" as "WPA-PSK / WPA2-PSK". Set a high-level password, such as a password containing numbers, uppercase and lowercase letters, and special characters (and it is recommended to record it), which can effectively prevent the password from being cracked