ntroduction to Firewalls:

• Firewalls filter incoming and outgoing network traffic.

Using UFW (Uncomplicated Firewall):

• Enable UFW:

  sudo ufw enable

• Allow specific services:

  sudo ufw allow ssh
  sudo ufw allow 80/tcp

• Deny a service:

  sudo ufw deny 21

• View status:

  sudo ufw status

Using iptables:

• Add a rule to allow SSH:

  sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT

• Drop all other incoming traffic:

  sudo iptables -A INPUT -j DROP

• Save rules:

  sudo iptables-save > /etc/iptables/rules.v4