# Modify this file accordingly for your specific requirement.
# pcguide.vn
# 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
#BLOCK_THIS_IP=”x.x.x.x”
#iptables -A INPUT -s “$BLOCK_THIS_IP” -j DROP

# 4. Allow ALL 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

# 5. Allow incoming SSH only from a sepcific network
#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

# 6. Allow 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

# Allow incoming HTTPS
#iptables -A INPUT -i eth0 -p tcp –dport 443 -m state –state NEW,ESTABLISHED -j ACCEPT
#iptables -A OUTPUT -o eth0 -p tcp –sport 443 -m state –state ESTABLISHED -j ACCEPT

# 7. MultiPorts (Allow incoming SSH, HTTP, and 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

# 8. Allow 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

# 9. Allow outgoing SSH only to a specific network
#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

# 10. Allow 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

# 11. Load balance incoming HTTPS traffic
#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

# 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 eth0 is connected to internal network (192.168.1.x)
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT

# 16. Allow outbound DNS
#iptables -A OUTPUT -p udp -o eth0 –dport 53 -j ACCEPT
#iptables -A INPUT -p udp -i eth0 –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 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

# 19. Allow MySQL connection only from a specific network
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

# 20. Allow Sendmail or 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

# 21. Allow IMAP and 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

# 22. Allow POP3 and 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

# 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 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

# 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

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