Strong IPTABLES Configuration [CentOS]

A persistent IPtables Firewall, for securing your server.









1. Reset all rules (F) and chains (X), necessary if have already defined iptables rules
iptables -t filter -F
iptables -t filter -X

2. Start by blocking all traffic
iptables -t filter -P INPUT DROP
iptables -t filter -P FORWARD DROP
iptables -t filter -P OUTPUT DROP

3. Keep established connexions
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

4. Allow loopback
iptables -t filter -A INPUT -i lo -j ACCEPT
iptables -t filter -A OUTPUT -o lo -j ACCEPT

5. HTTPS
iptables -t filter -A OUTPUT -p tcp --dport 443 -j ACCEPT
iptables -t filter -A INPUT -p tcp --dport 443 -j ACCEPT

6. To allow SSH from specific IP Address
iptables -t filter -A INPUT -p tcp -s YourIP --dport 22 -j ACCEPT
iptables -t filter -A OUTPUT -p tcp --dport 22 -j ACCEPT

etc,

note : Just allow the required course.