How to make a server in non-whitelist mode.

So, a player by the steam name of Andy.B got into one of his friends accounts (Andy’s friend shared his password with Andy, but now he has changed it due to the incident.) and decided to minge our server by demoting every player on that was staff, banning them, changing a lot of things, and put the server into whitelist mode. (Our server runs on Clockwork for Half-Life 2 Roleplay.) My question is, how do you make a server in non-whitelist mode.