Use a power conditioner without joules. Both Panamax and Furman (same parent company) have LiFT and SMP. You want SMP enabled surge devices. Anything with a joule rating is second tier stuff.
If your Ethernet cable is very long it might pick up an induced lightning strike.
There are a couple of suggestions:
If your network enters your home from coax, put a gas discharge coaxial protector on the outside of the home. On the inside use one of two things:
- Ethernet/optical converters
- Ethernet isolators (hospital grade)
I use two Ethernet/optical converters back to back to isolate my internal router from the cable modem. The Ethernet isolator ($45-$150) is used for particularly long Ethernet runs. Don’t use Ethernet surge protectors that need to be grounded. They tend to make the problem worse.