To block computer and mobile devices from connecting to your Netgear 779, follow the below steps:
Launch a web browser from a computer or wireless device that is connected to the network.
A login screen displays.
Enter the password in the Sign In field.
The default password is attadmin. The password is case-sensitive.
A list of devices connected to the main Wi-Fi and guest Wi-Fi networks displays in the right column of the screen.
Click the device name.
The device details display.
Click the Block Device button.
When prompted, click the Block Device button again. The device cannot access your Wi-Fi network.