The fat warning about optics make me realize a fibre optic cable can transmit light straight to the ISP's box (or can it?), and that it might be possible to shoot a laser to do some damage at the other end of a communication link, however little.
You could also connect a high voltage high current capable power supply to phone lines or coaxial cable and cause some damage. But it is immediately clear where it comes from!
That makes me think of this Danger 5 scene: https://www.youtube.com/watch?v=rDhrjKZprOo