从供选择的答案中，选出应填入下面叙述中______内的最确切的解答。 Basically,a firewall is a (1) process or a set ofintegrated processes that runs on a router or (2) to control the flow of networked application traffic (3) through it.Typically, firewalls are placed on the entry point to a (4) network such as the Internet. They could be considered traffic cops. The firewall's (5) is to ensure that all communication between an organization's network and the Internet conform to the organization's security policies.