Some years ago my home network was zapped with a lightning strike that came in via the coaxial cable. Modem, router, and two switches died to save my computers. In military designs, we used opto-isolators to shield sensitive circuits from attack.
Despite the hysteria, this is not a 'broad attack threat'. The attacker needs physical access to the network, and will probably only compromise part of the network due to the energies and damage modes involved. Unless he's Nikola Tesla and carrying his own lightning bolt. Then all bets are off.
I do recommend that you isolate your network from power threats with surge suppressors on your coax line or RJ-45 line from your ISP, and of course your power lines.