12.0

When a computer attempts to connect to another computer, the firewall compares
the connection type with the firewall rules. The firewall automatically checks all
the inbound traffic packets and outbound traffic packets against the rules. The
firewall allows or blocks the packets according to the rules.
Firewall rules are processed sequentially, from highest to lowest priority (from
top to bottom in the rules list). If the first rule does not specify how to handle a
packet, the firewall inspects the second rule. This process continues until the
firewall finds a match. When the firewall finds a match, it takes the action that
is specified in the rule. Subsequent lower priority rules are not inspected.
You can order rules according to exclusivity. The most restrictive rules are
evaluated first, and the most general rules are evaluated last. For example, you
should place the rules that block traffic near the top of the rules list. The rules
that are lower in the list might allow the traffic.
You can use triggers such as applications, hosts, and protocols to define complex
rules. For example, a rule can identify a protocol in relation to a destination
address. When the firewall evaluates the rule, all the triggers must be true for a
positive match to occur. If any trigger is false for the current packet, the firewall
does not apply the rule.
You can enable and disable firewall rules. The firewall does not inspect disabled
rules.
Table 14-2 lists the rule parameters that describe the conditions in which a network
connection is allowed or blocked.
Table 14-2
Firewall rule parameters
DescriptionParameter
The name of the firewall rule.Name
This parameter specifies what actions the firewall takes when it
successfully matches a rule.
The actions are as follows:
■ Allow
The firewall allows the network connection.
■ Block
The firewall blocks the network connection.
Action
Managing firewall protection
How the firewall works
130