With OPSecurity you can specify usernames that are allowed to have OP or certain permissions. If someone enters the server with OP who is not on this whitelist, Optional can be kicked or have OP removed.
This plugin also protects players from getting OP via unauthorized ways, e.g. hacked client, because only players who are on the OP whitelist can get OP with the command /op.
You can also use a timer that checks every few seconds (adjustable) if there is a player with OP or a permission on the server who is not on the whitelist.
Please note that you can only give OP via the console to players who are on the whitelist!
