Configuring is easy, just point to a gRPC server endpoint. Implementing the spam filter is left as an exercise for the reader... Big opportunity for projects to do stuff here. Mine isn't open source cause it is a bit too hacky to support at the moment (I have some homebrew jobs that analyze events for a bayes model).
Discussion
nostr.band has a spam list API that I was thinking about leveraging but not sure how well it works.
This could be of interest. https://github.com/blakejakopovic/nostr-spam-detection
Worth noting that spam or flood attacks don’t just come in the form of kind 1/42. You need protection against other non-content focused kinds too.