At present, Firewall is generally known as the security tool for network system. In fact, we also have other types of security tool. In principle, a firewall works by blocking certain incoming and outgoing packets in the network. The firewall filters packets according to predefined policy set by network administrator. However, in terms of additional layer of protection, most firewalls are not capable of analyzing packets except ones that incorporate IPS (Intrusion Prevention System) and IDS (Intrusion Detection System).