Why a Web Application Firewall (WAF) Is Still Needed When You Have a Next‑Generation Firewall (NGFW)

Introduction

Customers often ask, “If I already have a Next‑Generation Firewall (NGFW), why do I need a Web Application Firewall (WAF)?” This blog post explains the distinction between the two solutions, focusing on the added value a WAF can provide.

What Is a Web Application?

A web application is an application stored on a remote server and delivered over the Internet via a browser interface. Early websites were static pages, limiting user interaction. In the 1990s, server‑side scripting enabled dynamic interaction, giving rise to e‑commerce, web‑mail, online banking, blogs, forums, and custom platforms that rely on HTTP(S) for communication.

Modern web applications are increasingly complex, built with HTML5, Java, JavaScript, PHP, Ruby, Python, ASP.NET, etc., and often connect to backend databases that store sensitive business data. This makes them attractive targets for attackers, presenting a significant security challenge.

What Is a Next‑Generation Firewall (NGFW)?

Traditional firewalls are limited to packet filtering, NAT, and VPN functions, making decisions based on ports, protocols, and IP addresses. NGFWs add contextual information—such as location, identity, and time—to make smarter security decisions. They also integrate URL filtering, anti‑virus/anti‑malware, and intrusion prevention system (IPS) capabilities, simplifying policy enforcement in complex environments.

What Is a Web Application Firewall (WAF)?

A WAF protects web servers and hosted applications from attacks at the application layer while also mitigating non‑volume network‑layer attacks. It focuses on traffic directed at public‑facing web applications and can provide virtual patches for insecure coding practices. Most WAFs are deployed in front of an Application Delivery Controller (ADC) and are highly customizable to the specific design of the protected application.

Threat lists such as OWASP Top 10, CWE/SANS Top 25, and WASC v2.0 demonstrate the breadth of web‑application vulnerabilities, underscoring the need for dedicated WAF technology.

What Additional Value Does the F5 WAF Provide?

Default NGFW or IPS signatures often disable many web‑application protections to avoid false positives and performance loss. F5’s WAF includes a dedicated engine that decodes and normalizes traffic using deep knowledge of web protocols and languages, and it leverages advanced SSL/TLS decryption/unloading to improve detection effectiveness.

On top of a robust attack‑signature database, F5 offers URL, parameter, cookie, and form protection, as well as a policy‑learning engine that maps client requests to signatures for whitelisting or blocking. It also employs techniques such as URL encryption, code injection protection, cookie signing, and custom error pages to mitigate CSRF and other threats.

Finally, F5’s WAF tracks user sessions to detect malicious activity that could disrupt normal business flows and includes advanced anti‑bot and anti‑DDoS engines. Optional features include single sign‑on, multi‑factor authentication, and pre‑authentication for web applications.

SecureLink Integration Approach

SecureLink, a leading European security integrator, recommends a serial deployment of F5 WAF and Palo Alto Networks NGFW to achieve optimal protection. Their experts are proficient with both vendors’ products and have a strong record of satisfied customers.

Conclusion

Palo Alto Networks’ NGFW secures network traffic and protects internal clients when accessing the Internet and internal applications. The F5 Web Application Firewall focuses on safeguarding custom web applications from application‑layer threats.

SecureLink’s best‑practice is to implement F5 WAF and Palo Alto NGFW in series at the internet edge, combining F5’s SSL/TLS offloading and web‑application protection with Palo Alto’s IPS and anti‑virus capabilities.

In summary, WAF protects web applications while NGFW protects the network. Enterprises that rely heavily on web‑based applications can benefit greatly from a WAF, and in most cases both solutions should be deployed together.