How to not be a doormat?

I'm in a group of 6. Me, my friend, normal guy, n 3 assholes. These 3 ass rarely talk to me, but whenever the do, they talk as if I'm not worth of their time. They act like they're on top n talk to me like I'm an ant. Always shouting, not caring just a bit. "Hey, go **" I'm not ur maid?? we've been together (as a group) for more than 4 years.. i usually just ignore what they say and act they don't exist but my friend WILL be the target of their foul mouth if i ignore them.. any tips on how to handle them?