(also WAF, web application firewall)
Application firewall definition
An application firewall is a cybersecurity tool that protects applications from layer attacks, such as SQL injection, cross-site scripting (XSS), or cookie poisoning. It does so by governing traffic to and from an application or service. A firewall uses a series of configured policies to determine whether to allow or block communications traveling to or from an app.
Application firewall types
- Software firewall: a host-based firewall solution installed on the same web server as the apps they protect.
- Hardware firewall: this device plugs directly into a web server and inspects data packets before they reach the network.
- Cloud-based firewall: uses a cloud server and is sometimes called a proxy firewall. Generally, cloud-based firewalls have more capacity and provide easier traffic load management than software or hardware firewalls.
How application firewalls protect apps
- An application firewall analyzes each HTTP/S request at the application layer using a set of policies to determine whether traffic is safe or malicious.
- If the traffic is malicious, the firewall will filter, monitor, and block it from entering the web application.
- Application firewalls also prevent unauthorized data from leaving the application.
- Organizations use them as the first defense against common application vulnerabilities.