Newbie here. I just bought a new to me RV and have been researching surge protectors, which are not cheap. How do you stop somebody from just taking it? Same with the water filter.
It’s certainly not common at most campgrounds. I’ve never had one stolen either.
That said, you could use a short cable lock. You run it around the cord (or through the handle if there is one) of the surge protector and around the power pedestal. It does not make it theft-proof, but it turns a quick grab into a hassle, which is usually enough.