"Plus! Muffin" was a codename, not an actual thing
, as for the plugin, Norton detects it AFTER its on your system, so this will defend before it gets on your system. As for Automatic Blocking, that will only be used in situations in which it is almost for SURE a virus (ex. W32.Annoying.worm, Pic(1)(3)(2)(4).exe). Others you will be given the choice of what to do with the file.
Not all plugin developers are taken, you seem to have missed one