Here you’ll learn to setup ufw in linux to forbid connections from different ports.

UFW

UFW, or Uncomplicated Firewall, is an interface to iptables that is geared towards simplifying the process of configuring a firewall.
If your distro don’t have ufw, install it:

sudo apt-get install ufw

Then, we have options like:

• Enable/Disable firewall:

  sudo ufw enable
  sudo ufw disable
  

• Show status and detailed status:

  sudo ufw status
  sudo ufw status verbose
  

• Show rules list numbered:

  sudo ufw status numbered
  

• Blocks/Allows all incoming LAN traffic from internet:

  sudo ufw default deny incoming
  sudo ufw default allow incoming
  

• Blocks/Allows all outgoing LAN traffic to internet:

  sudo ufw default deny outgoing
  sudo ufw default allow outgoing
  

• Blocks/Allows connections through the port 45 (like ssh):

  sudo ufw deny 45
  sudo ufw allow 45
  

• Blocks/Allows connections from a specific ip:

  sudo ufw deny from 52.35.156.45
  sudo ufw allow from 52.35.156.45
  

• Blocks/Allows connections from a specific ip through a specific port 45:

  sudo ufw deny from 52.35.156.45 to any port 45
  sudo ufw allow from 52.35.156.45 to any port 45
  

• Blocks/Allows connections from a specific subnet (any using a ip in range 192.35.156.1 - 192.35.156.254):

  sudo ufw deny from 192.35.156.0/24
  sudo ufw allow from 192.35.156.0/24
  

• Blocks/Allows connections through the port 45 from a specific subnet (any using a ip in range 192.35.156.1 - 192.35.156.254):

  sudo ufw deny from 192.35.156.0/24 to any port 45
  sudo ufw allow from 192.35.156.0/24 to any port 45
  

• Blocks/Allows connections through the port 53 on TCP/UDP:

  sudo ufw deny 53/udp
  sudo ufw allow 53/udp
  sudo ufw deny 53/tcp
  sudo ufw allow 53/tcp
  

• Blocks/Allow a port ranges on tcp/udp:

  sudo ufw allow 6000:6007/tcp
  sudo ufw allow 6000:6007/udp
  

• Blocks/Allows Connections to a Specific Network Interface (e.g. eth0:

  sudo ufw deny in on eth0 to any port 15
  sudo ufw allow in on eth0 to any port 15
  

• Delete a Rule by number(for example, the 2th rule on the list):

  sudo ufw delete 2
  

• Delete rule (delete rule http and 2044):

  sudo ufw delete allow http
  sudo ufw delete allow 2044
  

• Reset (by default) configuration:

  sudo ufw reset