People making themselves admins on my clans server

[zootia 0]

How do you set it so that people cannot make themselves admins on our server?

We would be playing evo, and clear half the map for several hours. Then, when we go to bed or take a break, some pubber comes in and votes himself admin and resets the map.

We do not want to put a password on the server, because we do want pubbers coming in and playing with us. However, we do NOT want them taking over the server and resetting/changing maps. I know it is possible to lock admin rights, as I've seen it done before on many servers.

Can anybody tell me how to do it?

[Placebo 29]

This is a multiplayer question not a troubleshooting one, moving to MP