Linux Security The Complete Iptables Firewall Guide Free Download Apr 2026

iptables-save > /etc/iptables/rules.v4 To load iptables rules, you can use the iptables-restore command:

iptables -A INPUT -p tcp --dport 22 -j ACCEPT This rule allows incoming TCP traffic on port 22 (the default SSH port). To block incoming HTTP traffic, we can add the following rule: iptables-save > /etc/iptables/rules

iptables -A OUTPUT -p udp --dport 53 -j ACCEPT This rule allows outgoing UDP traffic on port 53 (the default DNS port). To save iptables rules, you can use the iptables-save command: To allow outgoing DNS traffic, we can add

iptables -A INPUT -p tcp --dport 80 -j DROP This rule drops incoming TCP traffic on port 80 (the default HTTP port). To allow outgoing DNS traffic, we can add the following rule: To allow outgoing DNS traffic

By following this guide, you should now have a solid understanding of iptables and how to use it to secure your Linux system. As a bonus, we’ve created an iptables cheat sheet that you can download for free.