Is it possible that they may have used a type of hardware backdoor? Something that would be connected to the router, or back of the computer using the lan or us

Is it possible that they may have used a type of hardware backdoor? Something that would be connected to the router, or back of the computer using the lan or usb port? None of that would show up in any logs or files, and it would get around any password protection and encryption on the actual computer, the only evidence would be from monitoring router traffic. A usb bug would be something that would transmit via wifi, but it would need to be connected directly to your computer to work. Also check inside the computer for anything unusual.