说明：  本文介绍了Dos(Denial of severance 拒绝服务)和Ddos(Distributed Denial of Severance 分布式拒绝服务)网络攻击的原理和c语言实现。并且在着重分析SYN-flooding的基础之上，介绍了UDP-flooding和Icmp-flooding攻击，并做出比较。最后，就软件防火墙对于Dos Ddos攻击的过滤给出了相应对策。 关键字：Dos Ddos SYN-flooding 防火墙 tcp/ip协议
(Dos (Denial of severance Denial of Service) and Ddos (Distributed Denial of Severance distributed denial of service) network attack down on the principle and C Language. And the focus on analysis SYN-flooding basis, on the UDP-flooding and Icmp-flooding attacks, and to make more. Finally, on the firewall software for Dos Ddos attack filtering the corresponding countermeasures. Keywords : Dos Ddos SYN-flooding firewall tcp/ip agreement)