List firewalls on the local machine

Question

In Windows besides the Windows firewall a user could have installed a firewall program, or there is another service listening to that port.

In Ubuntu how can I see what blocks/filters open ports? Iptables rules? What about outbound connections?

thanks!

Answer 1

In Linux, all the firewalls are actually interfaces to setting up the rules of the kernel iptables.

To list all rules, type

sudo iptables -S

You can also see what firewall packages are installed by writing

dpkg -l | grep -i firewall

Answer 2

To list rules on local machine use

sudo iptables -L -n

Ubuntu is shipped with firewall(ufw), which is not enabled by default

• To check status of firewall:sudo ufw status
  
• To enable: sudo ufw enable
  
• To disable: sudo ufw disable
  
• To allow traffic on port: sudo ufw allow <port_num>
  
• To block a port: sudo ufw block <port_num>
  

To check what outbound connections are running use command

sudo lsof -i -P -n