You should have a "011" short code in the ARS table...there is just a tick box to add Force Account code. Then just create your Account Codes...

BUT...

Is your IPO on the public internet? Does Manager, Operator and Administrator have their default passwords? Is auto create Ext turned on for ANY interface?

I would look at security from a system wide perspective....if they can break into it...account codes will only hold them off for so long.