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25 个常用的 Linux iptables 规则

  1. 删除所有现有规则
  iptables -F
  1. 设置默认的 chain 策略
iptables -P INPUT DROP

iptables -P FORWARD DROP

iptables -P OUTPUT DROP
  1. 阻止某个特定的 IP 地址
#BLOCK_THIS_IP="x.x.x.x"

#iptables -A INPUT -s "$BLOCK_THIS_IP" -j DRO
  1. 允许全部入站的(incoming)SSH
  
iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
  1. 只允许某个特定网络进来的 SSH
 
#iptables -A INPUT -i eth0 -p tcp -s 192.168.200.0/24 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
  1. 允许入站的(incoming)HTTP
iptables -A INPUT -i eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -o eth0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT
  1. 多端口(允许进来的 SSH、HTTP 和 HTTPS)
  
iptables -A INPUT -i eth0 -p tcp -m multiport --dports 22,80,443 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -o eth0 -p tcp -m multiport --sports 22,80,443 -m state --state ESTABLISHED -j ACCEPT
  1. 允许出站的(outgoing)SSH
  
iptables -A OUTPUT -o eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A INPUT -i eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
  1. 允许出站的(outgoing)SSH,但仅访问某个特定的网络
  
#iptables -A OUTPUT -o eth0 -p tcp -d 192.168.101.0/24 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A INPUT -i eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
  1. 允许出站的(outgoing) HTTPS
  
iptables -A OUTPUT -o eth0 -p tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A INPUT -i eth0 -p tcp --sport 443 -m state --state ESTABLISHED -j ACCEPT
  1. 对进来的 HTTPS 流量做负载均衡
  
#iptables -A PREROUTING -i eth0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 0 -j DNAT --to-destination 192.168.1.101:443

#iptables -A PREROUTING -i eth0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 1 -j DNAT --to-destination 192.168.1.102:443

#iptables -A PREROUTING -i eth0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 2 -j DNAT --to-destination 192.168.1.103:443
  1. 从内部向外部 Ping
  
iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT

iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT
  1. 从外部向内部 Ping
  
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT

iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT
  1. 允许环回(loopback)访问
  
iptables -A INPUT -i lo -j ACCEPT

iptables -A OUTPUT -o lo -j ACCEPT
  1. 允许 packets 从内网访问外网
  
if eth1 is connected to external network (internet)

if eth0 is connected to internal network (192.168.1.x)

iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT
  1. 允许外出的 DNS
  
iptables -A OUTPUT -p udp -o eth0 --dport 53 -j ACCEPT

iptables -A INPUT -p udp -i eth0 --sport 53 -j ACCEPT
  1. 允许 NIS 连接
  
rpcinfo -p | grep ypbind ; This port is 853 and 850

#iptables -A INPUT -p tcp --dport 111 -j ACCEPT

#iptables -A INPUT -p udp --dport 111 -j ACCEPT

#iptables -A INPUT -p tcp --dport 853 -j ACCEPT

#iptables -A INPUT -p udp --dport 853 -j ACCEPT

#iptables -A INPUT -p tcp --dport 850 -j ACCEPT

#iptables -A INPUT -p udp --dport 850 -j ACCEPT
  1. 允许某个特定网络 rsync 进入本机
  
#iptables -A INPUT -i eth0 -p tcp -s 192.168.101.0/24 --dport 873 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 873 -m state --state ESTABLISHED -j ACCEPT
  1. 仅允许来自某个特定网络的 MySQL 的链接
  
#iptables -A INPUT -i eth0 -p tcp -s 192.168.200.0/24 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 3306 -m state --state ESTABLISHED -j ACCEPT
  1. 允许 Sendmail 或 Postfix
  
iptables -A INPUT -i eth0 -p tcp --dport 25 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -o eth0 -p tcp --sport 25 -m state --state ESTABLISHED -j ACCEPT
  1. 允许 IMAP 和 IMAPS
  
#iptables -A INPUT -i eth0 -p tcp --dport 143 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 143 -m state --state ESTABLISHED -j ACCEPT

#iptables -A INPUT -i eth0 -p tcp --dport 993 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 993 -m state --state ESTABLISHED -j ACCEPT
  1. 允许 POP3 和 POP3S
  
#iptables -A INPUT -i eth0 -p tcp --dport 110 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 110 -m state --state ESTABLISHED -j ACCEPT

#iptables -A INPUT -i eth0 -p tcp --dport 995 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 995 -m state --state ESTABLISHED -j ACCEPT
  1. 防止 DoS 攻击
  
iptables -A INPUT -p tcp --dport 80 -m limit --limit 25/minute --limit-burst 100 -j ACCEPT
  1. 设置 422 端口转发到 22 端口
  
#iptables -t nat -A PREROUTING -p tcp -d 192.168.102.37 --dport 422 -j DNAT --to 192.168.102.37:22

#iptables -A INPUT -i eth0 -p tcp --dport 422 -m state --state NEW,ESTABLISHED -j ACCEPT

#iptables -A OUTPUT -o eth0 -p tcp --sport 422 -m state --state ESTABLISHED -j ACCEPT
  1. 为丢弃的包做日志(Log)
  
iptables -N LOGGING

iptables -A INPUT -j LOGGING

iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables Packet Dropped: " --log-level 7

iptables -A LOGGING -j DROP
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