Verizon FSNO21VA User Manual page 69

SECURITY & FIREWAll
Each request for a service that the firewall receives is checked
against the firewall rules to determine whether the request should
be allowed to pass through the firewall. If the request is permitted to
pass, all subsequent data associated with this request or session is
also allowed to pass, regardless of its direction.
For example, when accessing a website on the internet, a request
is sent to the internet for this site. When the request reaches your
Gateway, the firewall identifies the request type and origin, such
as HTTP and a specific computer in the local network. Unless your
Gateway is configured to block requests of this type from this
computer, the firewall allows this type of request to pass to the
internet.
When the website is returned from the web server, the firewall
associates the website with this session and allows it to pass;
regardless HTTP access from the internet to the local network is
blocked or permitted. It is the origin of the request, not subsequent
responses to this request, which determines whether a session can
be established.
5.0a/ SETTING FIREWALL CONFIGURATION
You can select a normal, high, or low security level to limit, block, or
permit all traffic. The following table shows request access for each
security level.