The Security tab is needed to specify various limitations for the external connection.
The Firewall page contains basic settings of the SPI Firewall. On the VPN Passthrough page you can limit the passing of traffic through different types of VPN channels.
Access Restrictions Section
There is only one page with settings on the Access Restrictions tab. It is called Internet Access Policy.
Here you can find settings pertaining to security and restrictions of the connection to the outer world. You can either limit the access to the external network or prohibit it altogether (this can all be done by a schedule or for individual machines).