Traditional firewalls just simply reject the data packets or inform the administrator of network via e-mail when recognizing the network attack, so they lack the mechanism of responding to the attack in real time.

• 传统的防火墙在发现网络攻击时，或只是简单的做包拒绝，或只是通过电子邮件通知网络管理人员，缺乏在第一时间对网络攻击的应变机制。