WAF vs. Firewall: What are the differences?
Both essential parts of any security program, WAFs and firewalls help to protect networks and systems at different levels and from different types of threats.
What is a WAF?
A Web Application Firewall (WAF) is a specialized security solution that shields a web application from the internet, safeguarding the server by detecting and blocking malicious HTTP and HTTPS traffic to and from a web service.
When properly configured and enabled, a WAF prevents application-layer (Layer 7) attacks that exploit web application vulnerabilities, including those listed by OWASP, like SQL injection, cross-site scripting (XSS), and HTTP protocol violations.
What is a Firewall?
A network firewall is a network security device or software that monitors and filters incoming and outgoing traffic based on predefined rules. It primarily operates at network (Layer 3) and transport (Layer 4) levels of the OSI model. Its main purpose is to block unauthorized access while allowing legitimate connections, protecting infrastructure from threats like port scans, malware, or intrusion attempts.
What are the differences between a WAF and a Firewall?
The table below shows key differences between a WAF and a firewall from where they operate to how they operate and what purpose they serve.
Category | WAF | Firewall |
Purpose | Protects web applications from attacks targeting application logic | Protects networks and systems from unauthorized access and traffic |
OSI Layer | Operates at Layer 7 (Application Layer) | Operates mainly at Layer 3 (Network) and Layer 4 (Transport) |
Traffic Type | Inspects HTTP/HTTPS requests and responses | Monitors all network traffic, including TCP, UDP, and ICMP |
Threat Focus | Guards against SQL injection, XSS, file inclusion, Layer 7 DDoS, and API abuse | Defends against unauthorized access, malware, port scans, and network-layer DDoS |
Analysis Method | Uses contextual and behavioral analysis of web requests and payloads | Uses packet filtering and rule-based inspection |
Deployment Location | Placed in front of web servers or applications | Typically deployed at the network perimeter or between segments |
Configuration Complexity | Application-specific; often managed by DevSecOps or AppSec teams | Network-wide; typically managed by network security admins |
Integration | Often integrated with CDNs, API gateways, and DDoS mitigation | Often integrated with VPNs, intrusion prevention systems (IPS), and routers |
Use Case | Protecting a website or API from web exploits | Blocking unauthorized traffic from entering a corporate network |
Best For | Businesses running web apps, APIs, or SaaS platforms | Organizations managing internal networks, data centers, or cloud infrastructures |
What are the benefits of a WAF?
A WAF should be part of any robust security program. They help provide protection against known vulnerabilities, handle large volumes of traffic, and
Good solutions require very little effort to get up and running. More specifically, the benefits of using a WAF include:
Data protection
WAFs intercept all incoming HTTP requests, helping to prevent unauthorized access and avoid data breaches.
DDoS mitigation
WAFs can help protect web applications from distributed denial-of-service (DDoS) attacks. You can also use a dedicated DDoS solution for this.
Protection against Application Layer Attacks
WAFs help block common application-layer attacks like SQL injection and cross-site scripting (XSS).
Compliance
WAFs help an organization remain compliant, with requirements like PCI DSS.
Better overall security posture
WAFs are a great way to improve your overall security posture, preventing threats or vulnerabilities from impacting your org.
Increased visibility
WAFs can help you get better insights into your web traffic and any potential threats.
Access Control
WAFs can help you to enforce access controls, meaning unauthorized users/traffic can’t access your systems.
What are the benefits of a firewall?
Firewall serves as the foundation of network security. It monitors and filters traffic between internal (trusted) and external (untrusted) networks, ensuring that only legitimate data passes through. Use of a firewall yields various benefits to a security program:
Prevention of unauthorized access
Traditional firewalls enforce access control policies that prevent unauthorized users, systems, or devices from entering your network. They also help keep internal systems from direct exposure to the internet.
Network traffic filtering
Firewalls examine data packets and filter them based on IP addresses, protocols and ports. This helps to ensure only ‘approved’ network communications can occur and limits anything falling outside of expected or allowed behavior.
Prevention of external attacks
By stopping malicious traffic at the perimeter, firewalls help shield against a variety of concerns (think spoofing or unauthorized remote access). They can also help prevent net-work layer attacks like DDoS and SYN flood attacks.
They are the gatekeepers of a business’ critical internal workings.
Enhanced network performance and stability
By filtering unwanted or unnecessary traffic, firewalls help to minimize network congestion, freeing up bandwidth for legitimate (wanted) services and applications.
Support of a layered security strategy
Firewalls are the foundation to a defense-in-depth security strategy. Working in partnership with other critical security tools (WAFs, antivirus solutions, and intrusion detection systems), firewalls form the outermost layer of a multi-pronged security program.
Should you use a WAF and firewall together?
So can a WAF replace a firewall, or vice versa? No…
Neither security solution can serve as a substitute for the other, since each serves a specific and very important purpose. A firewall defends your network infrastructure while a WAF defends your web application. Use of both together in a layered security approach (commonly called defense in depth) is the best approach.
So you need both a WAF and a firewall together.
This is particularly true for organizations that have web applications and APIs (basically everyone).
While firewalls help block more general threats to a network and prevent unauthorized connections, a WAF provides a deeper layer of security, helping block application=level vulnerabilities that firewalls are unable to detect. In tandem, using a WAF plus a firewall provides the most comprehensive security coverage for any modern security program.
How Fastly can help
When choosing a WAF provider, it is essential to select one with global coverage, powerful detection, and integration capabilities tailored to modern infrastructure. Fastly's Next-Gen WAFis designed from the ground up with these features in mind. As the world's largest global edge cloud platform, it sits within milliseconds of users worldwide.
This strategic positioning allows Fastly to protect websites and applications faster than traditional WAFs. Inspecting traffic close to end users quickly limits the level threats can penetrate, helping to block attacks before they ever reach the origin servers.