anti spawner

 <event>
<outcome affected_mobs="zombie, skeleton, spider, blaze" affected_worlds="world, world_nether">
<conditions>
<spawn_reason>spawner</spawn_reason>
</conditions>>
    <action_group>
      <actions>
        <remove/>
		<drop_exp>1</drop_exp>
      </actions>
    </action_group>
</outcome>
</event>