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Firewalls play an important roll to control Network Traffic.

The Linux kernel includes the Netfilter subsystem which is used to control network incoming and outgoing traffic.

Linux firewalls utilise Netfilter. The administrator tells Netfilter how to treat data packets by configuring rules in iptables, a configuration file.

In Ubuntu, we use ufw as a configuration tool for iptables.


“the friendly way to create a firewall” ufw: Uncomplicated firewall

installing ufw :

sudo apt-get install ufw

Enable ufw and restart the server to take effect:

You will not be able to restore the SSH connection until you configure ufw to allow SSH traffic:

sudo ufw allow 22



sudo ufw deny 22

ufw, examples of rules

Delete a rule:

sudo ufw delete deny 22

Allow access from a host to port 22 of any IP address on this host:

sudo ufw allow proto tcp from to any port 22


Allow all HTTP traffic:

sudo ufw allow http


Use --dry-run to show the rule corresponding to a directive:

Disable the firewall:

sudo ufw disable

See ststus:

sudo ufw status


See ditailed status:

sudo ufw status verbose

Application integration, predefined rules. Apply like this “sudo ufw allow Postfix” and “sudo ufw app info Postfix” to view rule details:


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