| Before you can even understand an answer, what does a destructive surge seek? What is the connection? An electric current from cloud, through appliances, to earth ground, and then to earthborne charges maybe miles away.|
What does a surge protector do? From the NIST (US government research agency):
> You cannot really suppress a surge altogether, nor "arrest" it.
> What these protective devices do is neither suppress nor arrest a
> surge, but simply divert it to ground, where it can do no harm.
Any protector that will stop or absorb a surge is a scam. Will that silly little protector that a majority recommend somehow stop what three miles of sky could not? Will its few hundred joules absorb surge energy that is hundreds of thousands of joules? That is the popular myth promoted by a clear majority. They believe only what they are told to believe. They must ignore what the NIST says.
A surge can be incoming on AC mains. That means everything in the house is confronted by an incoming surge. What is damaged? Well, what makes an outgoing connection to earth? It is electricity. No damage without the outgoing path. An incoming path with no outgoing path means no damage.
What does a plug-in protector do? Gives a surge MORE paths to find earth destructively via appliances.
Science has been well proven for over 100 years - and still a clear majority will instead recommend the scams. You must earth a surge before it can enter the building.
Either surge energy is absorbed harmlessly in earth - ie one 'whole house' protector for everything. Or that energy goes hunting for earth destructively inside the building. Surge protection is about where that energy is dissipated.
Back to your question. What would an RG-45 protector do? Nothing. All ethernet ports already contain significant surge protection. All appliances contain surge protection. You must earth the rare surge that can overwhelm hundreds (if not thousands) of already existing surge protection. A surge harmlessly dissipated in earth does not go hunting destructively for earth via household appliances.
Because so many don't know this 100+ year old knowledge. Because so many will recommend plug-in protectors when even the manufacturer does not claim that protection in numeric specs. Then a majority will promote popular myths - as if a protector will stop what three miles of sky could not.
Responsible homeowners install 'whole house' protectors from the more responsible companies such as General Electric, Square D, Intermatic, Leviton, Keison, Polyphaser, etc. The Cutler-Hammer solution sell in Lowes for less than $50. But again, the question is always about the energy. Where is energy absorbed? Essential for any protector is that 'less than 10 foot' connection to earth.
A protector is only as effective as its earth ground.