Created Friday 13 January 2017
# https://gist.github.com/virtualstaticvoid/1024546
# Change wlp2s0 to your network devices if needed
# 1. Delete all existing rules
$ iptables -F
# 2. Set default chain policies
$ iptables -P INPUT DROP
$ iptables -P FORWARD DROP
$ iptables -P OUTPUT DROP
# 3. Block a specific ip-address
$ iptables -A INPUT -s <IP_ADDRESS> -j DROP
# 4. Allow ALL incoming SSH
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
# 5. Allow incoming SSH only from a specific network
$ iptables -A INPUT -i wlp2s0 -p tcp -s <IP_ADDRESS>/24 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
# 6. Allow incoming HTTP
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT
# Allow incoming HTTPS
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 443 -m state --state ESTABLISHED -j ACCEPT
# 7. MultiPorts (Allow incoming SSH, HTTP, and HTTPS)
$ iptables -A INPUT -i wlp2s0 -p tcp -m multiport --dports 22,80,443 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp -m multiport --sports 22,80,443 -m state --state ESTABLISHED -j ACCEPT
# 8. Allow outgoing SSH
$ iptables -A OUTPUT -o wlp2s0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A INPUT -i wlp2s0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
# 9. Allow outgoing SSH only to a specific network
$ iptables -A OUTPUT -o wlp2s0 -p tcp -d <IP_ADDRESS>/24 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A INPUT -i wlp2s0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
# 10. Allow outgoing HTTPS
$ iptables -A OUTPUT -o wlp2s0 -p tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A INPUT -i wlp2s0 -p tcp --sport 443 -m state --state ESTABLISHED -j ACCEPT
# 11. Load balance incoming HTTPS traffic
$ iptables -A PREROUTING -i wlp2s0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 0 -j DNAT --to-destination <IP_ADDRESS>:443
$ iptables -A PREROUTING -i wlp2s0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 1 -j DNAT --to-destination <IP_ADDRESS>:443
$ iptables -A PREROUTING -i wlp2s0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 2 -j DNAT --to-destination <IP_ADDRESS>:443
# 12. Ping from inside to outside
$ iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT
$ iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT
# 13. Ping from outside to inside
$ iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
$ iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT
# 14. Allow loopback access
$ iptables -A INPUT -i lo -j ACCEPT
$ iptables -A OUTPUT -o lo -j ACCEPT
# 15. Allow packets from internal network to reach external network.
# if eth1 is connected to external network (internet)
# if wlp2s0 is connected to internal network (192.168.1.x)
$ iptables -A FORWARD -i wlp2s0 -o eth1 -j ACCEPT
# 16. Allow outbound DNS
$ iptables -A OUTPUT -p udp -o wlp2s0 --dport 53 -j ACCEPT
$ iptables -A INPUT -p udp -i wlp2s0 --sport 53 -j ACCEPT
# 17. Allow NIS Connections
# 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
# 18. Allow rsync from a specific network
$ iptables -A INPUT -i wlp2s0 -p tcp -s <IP_ADDRESS>/24 --dport 873 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 873 -m state --state ESTABLISHED -j ACCEPT
# 19. Allow MySQL connection only from a specific network
$ iptables -A INPUT -i wlp2s0 -p tcp -s <IP_ADDRESS>/24 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 3306 -m state --state ESTABLISHED -j ACCEPT
# 20. Allow Sendmail or Postfix
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 25 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 25 -m state --state ESTABLISHED -j ACCEPT
# 21. Allow IMAP and IMAPS
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 143 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 143 -m state --state ESTABLISHED -j ACCEPT
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 993 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 993 -m state --state ESTABLISHED -j ACCEPT
# 22. Allow POP3 and POP3S
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 110 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 110 -m state --state ESTABLISHED -j ACCEPT
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 995 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 995 -m state --state ESTABLISHED -j ACCEPT
# 23. Prevent DoS attack
$ iptables -A INPUT -p tcp --dport 80 -m limit --limit 25/minute --limit-burst 100 -j ACCEPT
# 24. Port forwarding 422 to 22
$ iptables -t nat -A PREROUTING -p tcp -d <IP_ADDRESS> --dport 422 -j DNAT --to <IP_ADDRESS>:22
$ iptables -A INPUT -i wlp2s0 -p tcp --dport 422 -m state --state NEW,ESTABLISHED -j ACCEPT
$ iptables -A OUTPUT -o wlp2s0 -p tcp --sport 422 -m state --state ESTABLISHED -j ACCEPT
# 25. Log dropped packets
$ 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