🔰Ports/Protocols: If the services running on a given port is intended for the public or network users, they are usually kept open. Otherwise they are blocked using the firewall so as to prevent intruders from using the open ports for making unauthorized connections.

🔰Specific words or phrases: A firewall can be configured to filter one or more specific words or phrases so that both the incoming and outgoing packets are scanned for the words in the filter.