If you see an unauthorized client in your router's mobile app or admin control panel, select the entry for that device. You should see the option to block, ban, or eject the device.

Update at 11:00 AM EST: All services except for the Admin control panel seem to be operational again. For the services with an orange dot, the outage time totaled just over an hour and a half.

It can be enabled for specific users or groups, or for the organization as a whole–giving the IT admin some control over how and where Google+ is used within the organization.

A good control panel will provide tools to create the desired functionality, look and feel you want for your site while allowing you to update it as your site evolves.