Every device has a unique MAC address.

You can allow only approved devices to connect.

Steps:

1. Find device MAC addresses (HP-Shut off, turn on, press F10 until Entering Setup Menu pops up on the bottom left corner of the screen)
   
   

2. Enter into router whitelist
   
   

3. Enable filtering
   
   

Note: Advanced attackers can spoof MACs, so this is extra protection — not primary.