You get an audio capcha ("This phone is protected by NoMoRobo. Press $NUMBER to prove you aren't a robot. Press $NUMBER to prove you aren't a robot. ... Good

You get an audio capcha ("This phone is protected by NoMoRobo. Press $NUMBER to prove you aren't a robot. Press $NUMBER to prove you aren't a robot. ... Goodbye.") $NUMBER is two randomly generated digits. Presumably one can feedback loop that into the reputation score. Honestly, though, I don't think this is a terribly likely attack.