> For the complete documentation index, see [llms.txt](https://docs.serverlessapigateway.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.serverlessapigateway.com/glossary/f/firewall.md). # Firewall A network security device that monitors and filters incoming and outgoing network traffic based on an organization's previously established security policies. A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. Firewalls establish a barrier between trusted internal networks and untrusted external networks, such as the internet. Firewalls operate at different layers of the network stack. Packet-filtering firewalls inspect individual packets based on IP addresses and ports. Stateful firewalls track the state of network connections. Application-layer firewalls (also called Web Application Firewalls or WAFs) inspect the content of HTTP requests and can block attacks like SQL injection, cross-site scripting, and request forgery. In API management, WAFs are commonly deployed alongside or integrated into API gateways. They inspect API requests for malicious payloads, enforce rate limits on suspicious traffic, and block known attack patterns. Cloud-based WAFs provided by platforms like Cloudflare can protect API endpoints without requiring any changes to backend infrastructure, filtering malicious traffic at the edge before it reaches origin servers. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.serverlessapigateway.com/glossary/f/firewall.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. 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.