Tường lửa Tường lửa đã được đề cập một số tiền công bằng trong các phần tiếp tục của chương này (và đã được đề cập trong các chương khác nhau khác). Tường lửa là một thiết bị điều khiển truy cập mạng được thiết kế để phủ nhận tất cả lưu lượng truy cập, ngoại trừ đó là một cách rõ ràng cho phép | 152 Network Security A Beginner s Guide Dual firewalls do increase the cost of the architecture and require additional management and configuration. FIREWALLS Firewalls have been mentioned a fair amount in the proceeding sections of this chapter and have been mentioned in various other chapters as well . A firewall is a network access control device that is designed to deny all traffic except that which is explicitly allowed. This definition contrasts with a router which is a network device that is intended to route traffic as fast as possible. Some will argue that a router can be a firewall. I will agree that a router can perform some of the functions of a firewall but one key difference remains A router is intended to route all traffic as fast as possible not to deny traffic. Perhaps a better way to differentiate a router and a firewall is to say that a firewall is a security device that can allow appropriate traffic to flow while a router is a network device that can be configured to deny certain traffic. In addition to this firewalls generally provide a more granular level of configuration. Firewalls can be configured to allow traffic based on the service the IP address of the source or destination or the ID of the user requesting service. Firewalls can also be configured to log all traffic. Firewalls can perform a centralized security management function. In one configuration the security administrator can define allowed traffic to all systems within an organization from the outside. While this does not alleviate the need to properly patch and configure systems it does remove some of the risk that one or more systems may be misconfigured and thus open to attack on an inappropriate service. Sensitive Internal Networks Firewalls should not be limited to use only on Internet connections. A firewall is a network access control device that can be used anywhere that access must be controlled. This includes internal networks that should be protected from other .
