Restrict access to server

[Mistmaker]

What's the best way to limit access to the server by invitation only? Currently I'm adding access by using the gm_ips field and then add the players account name, Account ID and IP.

Is their an easier way of doing this? Currently I enabled this server rule and use this script.

World:GMAccountIPList = true

INSERT INTO gm_ips (name,account_id,ip_address) VALUES ('xxxxxx','xxxxxxx','xxx.xxx.xxx.xxx');