Isabelle is the cybersecurity engineer for a medium$-$sized company. She is setting up a firewall for examining inbound network traffic for a variety of characteristics. While remote users working from home should be allowed access to network resources, malicious traffic should be blocked. To differentiate between the two, Isabelle is looking at factors such as whether the inbound traffic is a response to a previous request inside the network; whether it includes blocked domain names, IP addresses, and protocols; and whether it conforms to known malicious patterns or is otherwise abnormal. What is she setting up the firewall to practice?