There is the build in vb way - vboptions > server settings > *NIX Server Load Limit. Then there are various modifications you may install like -
Deny Unregistered Users When Load Is High - Load Deny (*Nix). Do a search for "load" or "server" "all mods" "titles only".
Also, in the future, please start your own thread instead of adding to an existing one. It helps to only have one topic per thread.