how do I stop mob spawners from working by using a command block/command?

I have a minecraft server that's based on defeating monsters and receiving power-ups. In this server a regular zombie, a skeleton, creeper or a spider is much faster and stronger than they usually are. For example you kill 100 zombies to get a higher attack damage or kill 100 spiders to get a better attack speed, and there are many more quests like so. But since minecraft has dungeons that have mob spawners, players could simply farm mobs and get their power-ups rather than defeating monsters that spawn naturally. So is there a command that stops a mob spawner from working completely? Or a command that stops a mob spawner from generating? pls help