# What is a Firewall A firewall is a fence between your computer or your internal network and the outside world or the Internet. A particular firewall implementation might use one or more of the methods listed here to provide that barrier. * Packet filtering * Stateful packet filtering * User authentication * Client application authentication At a minimum, a firewall will filter incoming packets based on parameters such as packet size, source IP address, protocol, and destination port. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://wiki.zacheller.dev/network-security/courses/isci-cnss-course/fundamentals-of-firewalls/what-is-a-firewall.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.