Through → you can access into the eBox's proxy HTTP general configuration.
At the configuration window these options are detailed:
If transparent proxy is enabled, every eBox user will use the transparent proxy without noticing it. If it is disabled, you should configure each browser to work through the proxy.
Transparent proxy feature is only working when eBox has at least an internal and an external interface
You can assign a proxy port. It will be used by the browsers, inside the network, to connect to Internet.
It is the default policy for the proxy users. Free (allow all) access, filter contents or always deny access can be selected. Later, this policy can be modified for each network object where you need an specific behaviour, as it is explained below
If you establish a configuration which denies access to administration interface from the machines connected to eBox, you should allow the host where you want to connect from, or you could lose the connection with the web interface.