System firewall configuration

To restrict traffic based on firewall rules, traffic should only be allowed into ports that need to be open for services. For example, secure web servers will need to provide access to TCP port 443 to most users, but they do not need Remote Desktop Protocol (RDP) or Secure Shell (SSH) management access from all source IPs.

For Windows, you can configure new inbound and outbound rules using advanced security options:

For Linux, sudo iptables -L lists your current rules in iptables. If you have just set up your server, you will have no rules and the output should be similar to the following screenshot: