As of December 1, 2013, all clients will be able to configure additional levels of "Access Control" security for their accounts. The new Access Control functionality can be enabled by navigating to "My Account > Access Control".
IP-Address Based Access Control:
Select the menu item "IP-Addresses" and simply enter an IP-address along with subnets, which will then only allow access to your account via the web Control Panel and/or via API through the provided IP-addresses (incl. Subnet).
Role-User Based Access Control:
Under role-user access in the Control Panel, you may define additional ACLs (Access Control List) to limit access for specific users. Please not that IP-address controls continue to be in effect on top of any Role-User restrictions.
Two Stage Login Authentication - COMING SOON:
In the first quarter of 2014, an enhanced two-stage login authentication process will be activated for even more account level security. More information will be provided as it is available.