Enforce firewall rules: Firewall rules are used to dictate what traffic can pass between the firewall and the internal network. Three possible actions can be taken based on the rule's criteria: block the connection (explicit deny), accept the connection, or allow the connection if conditions are met (such as it being secured). It is this last condition that is the most difficult to configure, and conditions usually end with an implicit deny clause. An implicit deny clause means that if the proviso in question has not been explicitly granted, access is denied.