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Web Application Firewall (WAF)

A web application firewall (WAF) provides specialized protection for web servers by detecting and blocking threats that standard firewalls are not designed to handle. It sits between external traffic and web applications, filtering attacks such as denial of service attempts before they reach the server.

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About this video

Web applications are disproportionately targeted by attackers compared to other systems, and a conventional network firewall lacks the application-layer visibility needed to defend against the full range of web-specific threats. A web application firewall (WAF) addresses this gap by inspecting HTTP traffic for malicious patterns and blocking attacks before they reach the server, operating as a specialized security control purpose-built for web environments. It is commonly deployed in a DMZ or screened subnet—a network segment that must remain accessible to outside users while still being protected—where a standard firewall alone would leave the web server exposed to application-layer exploits. By placing a WAF in front of web servers in this architecture, organizations gain a targeted layer of protection that complements existing network security controls without replacing them. Practical use cases include blocking denial of service attacks directed at a web application, where the WAF detects the anomalous traffic pattern and drops it before it can degrade or take down the service—a capability that falls outside what a traditional perimeter firewall is designed to provide.

What you'll learn

What's covered

Web Application Firewall (WAF)

Key terms

Web Application Firewall
WAF
A firewall that filters and monitors HTTP traffic to and from a web application to prevent attacks.
Firewall
A network security device that monitors and controls incoming and outgoing traffic based on predefined security rules.
Demilitarized Zone
DMZ
A network segment that sits between a trusted internal network and an untrusted external network, hosting public-facing services.
Denial of Service
DoS
An attack that floods a system or network with traffic to make it unavailable to legitimate users.
Network Segmentation
The practice of dividing a network into smaller segments to improve performance and limit the spread of security threats.

Topics

Web Application Firewall Network Security Dmz Application Layer Security Denial Of Service Protection Network Architecture

Transcript

Web application firewalls

Our web applications are going to be attacked more than a lot of other types of applications, so there are extra steps that we need to do to secure these web applications. One way that we can do that is through a web application firewall.

This is a common setup right here. We have a firewall with a network on the back end here, and then we have a DMZ network over here, the demilitarized zone, or a screened subnet. This is protected in a little different way than this is right here. We have to allow people in to get to these web servers right here, so we open a hole on that.

But here what we have is a standard firewall, and the standard firewall is great for some levels of security. But there are certain attacks that are going to happen against this web server right here that aren't going to be the same type of attacks that are going to happen against the rest of the network. So we may want a specialized firewall right there. We may want a web application firewall, or WAF.

In this case right here, let's say we've rolled out a web application firewall right here. Now this is going to look for certain types of behavior and certain types of traffic. For instance, if there's a denial of service attack that's being attempted on this server right here, a web application firewall can identify that and stop that traffic from hitting that application. So that's just one example of how a web application firewall can add extra protection to a web application that a regular firewall wouldn't be able to do.

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