httpd子进程不存在？

ApogeeZ

服务器是centOS4.2 +apache2+php5+mysql4\r\n突然间打开网页非常慢，top一下，发现httpd变成了zombie，查看error日志，提示说child process不存在\r\n用netstat -na一看，发现很多ip的状态是fin-wait，怀疑是遭到了DDOS攻击\r\n于是在/etc/rc.d/rc.local中添加\r\necho 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all\r\necho 1 >/proc/sys/net/ipv4/tcp_syncookies\r\necho \"1\" > /proc/sys/net/ipv4/tcp_syn_retries\r\necho \"1\" > /proc/sys/net/ipv4/tcp_synack_retries\r\necho 2280 >/proc/sys/net/ipv4/tcp_max_syn_backlog\r\necho 1 >/proc/sys/net/ipv4/tcp_fin_timeout\r\n\r\n在iptables里面添加\r\n#防止別人用ACK、SYN、FIN等等的封包來掃瞄\r\n-A RH-Firewall-1-INPUT -i eth0 -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP\r\n#防止 port scan\r\n# NMAP FIN/URG/PSH\r\n-A RH-Firewall-1-INPUT -i eth0 -p tcp --tcp-flags ALL FIN,URG,PSH -j DROP\r\n# Xmas Tree\r\n-A RH-Firewall-1-INPUT -i eth0 -p tcp --tcp-flags ALL ALL -j DROP\r\n# Another Xmas Tree\r\n-A RH-Firewall-1-INPUT -i eth0 -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP\r\n# Null Scan(possibly)\r\n-A RH-Firewall-1-INPUT -i eth0 -p tcp --tcp-flags ALL NONE -j DROP\r\n# SYN/RST\r\n-A RH-Firewall-1-INPUT -i eth0 -p tcp --tcp-flags SYN,RST SYN,RST -j DROP\r\n# SYN/FIN -- Scan(possibly)\r\n-A RH-Firewall-1-INPUT -i eth0 -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP\r\n#阻止空会话继续运行\r\n#-A INPUT -s ! 192.168.0.0/24 -p tcp ! --syn -m state --state NEW -j DROP\r\n-A RH-Firewall-1-INPUT -p tcp ! --syn -m state --state NEW -j DROP\r\n#防止Dos攻击\r\n-A RH-Firewall-1-INPUT -p tcp --dport 80 -m limit --limit 10/second --limit-burst 300 -j ACCEPT\r\n#防止 sync flood 攻擊的設定:\r\n\r\n-N synfoold\r\n-A synfoold -p tcp --syn -m limit --limit 1/s -j RETURN\r\n-A synfoold -p tcp -j REJECT --reject-with tcp-reset\r\n-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -j synfoold\r\n\r\n-N ping\r\n-A ping -p icmp --icmp-type echo-request -m limit --limit 1/second -j RETURN\r\n-A ping -p icmp -j REJECT\r\n-I RH-Firewall-1-INPUT -p icmp --icmp-type echo-request -m state --state NEW -j ping\r\n\r\n重启服务器，发现仍然很慢\r\n请教各位，这到底是怎么一回事？谢谢！