Web Application Firewall (WAF): Strengthening Web Application Security


Web Application Firewall (WAF)

A Web Application Firewall (WAF) serves as a vital security control that shields websites and web applications from cyberattacks. Think of it as a discerning doorman at an exclusive club, determining who gains access and who is denied.

Its role involves analyzing the traffic between the internet and the web application, effectively blocking any suspicious activities. Unlike traditional firewalls that focus on network protection, WAFs are specifically designed to combat web-based attacks.

To complement WAFs, a newer technology called Runtime Application Self-Protection (RASP) detects and halts assaults in real-time, right within the application itself.

Understanding Web Application Firewall (WAF)

A web application firewall, commonly known as WAF, acts as a shield for web applications by meticulously filtering and monitoring HTTP traffic between the web application and the Internet.

It provides protection against various types of attacks, including cross-site forgery, cross-site scripting (XSS), file inclusion, and SQL injection.

It operates as a defense mechanism at protocol layer 7 within the OSI model and is typically part of a comprehensive suite of tools that collectively offer robust defense against multiple attack vectors.

The Role and Function of a Web Application Firewall (WAF)

A WAF safeguards web applications by effectively filtering, monitoring, and blocking any malicious HTTP/S traffic destined for the application. By adhering to predefined policies, it distinguishes between secure and malicious traffic, preventing unauthorized data from leaving the application.

Similar to how a proxy server safeguards a client’s identity, a WAF acts as an intermediary to protect the web application server from potentially malicious clients, working in reverse proxy mode.

WAFs can be implemented as software, hardware appliances, or services, allowing flexibility to tailor policies based on the specific requirements of your web application or application portfolio.

While regular policy updates are often necessary to address new vulnerabilities, advancements in machine learning enable some WAFs to update themselves autonomously. This automated approach becomes increasingly crucial as the threat landscape grows in complexity and uncertainty.

What sets a WAF apart from a firewall?

A web application firewall (WAF) and a traditional firewall have distinct differences in terms of their scope and functionality. Let’s explore the contrasting features of these security measures:

WAF: Safeguarding the Application Layer A WAF is specifically designed to protect the application layer by analyzing each HTTP/S request at that layer. It operates with awareness of the user, session, and application, including the web applications and services they interact with.

Think of a WAF as the intermediary between the user and the application, scrutinizing all communications before they reach either party. WAFs ensure that only authorized actions, based on security policies, are allowed.

They serve as the initial line of defense for applications, especially in addressing the OWASP Top 10, which outlines common vulnerabilities in applications.

Top 10 Application Vulnerabilities:

  1. Injection Attacks
  2. Broken Authentication
  3. Sensitive Data Exposure
  4. XML External Entities (XXE)
  5. Broken Access Control
  6. Security Misconfigurations
  7. Cross-Site Scripting (XSS)
  8. Insecure Deserialization
  9. Using Components with Known Vulnerabilities
  10. Insufficient Logging and Monitoring

Web Attacks vs. Unauthorized Access

WAF solutions protect organizations from web-based attacks targeted at applications. Without a WAF, vulnerabilities in web applications could be exploited by attackers to breach the network. WAF security solutions shield enterprises from common web attacks, including:

  1. DDoS (Distributed Denial of Service): Attempts to disrupt a network or server by overwhelming it with excessive internet traffic, depleting resources. Defending against DDoS attacks can be challenging as the traffic may not always appear malicious.
  2. SQL Injection: Allows hackers to execute malicious SQL statements to manipulate the database server underlying a web application. This can bypass webpage authentication, retrieve database contents, and modify or delete records. SQL injection has been ranked as the top threat to web application security.
  3. Cross-Site Scripting (XSS): A web security flaw enabling attackers to compromise user interactions with web applications, impersonating legitimate users to gain unauthorized access to data and resources.

Network Traffic vs. Application Traffic

Traditional network firewalls focus on limiting or preventing unauthorized network access. Firewall policies define permitted network traffic, blocking any attempts outside of those defined rules. This helps prevent unauthorized network traffic and attacks from users or devices in less secure zones.

In contrast, a WAF specifically targets application traffic. It safeguards HTTP and HTTPS traffic and protects applications in internet-accessible network zones. This shields businesses from threats like cross-site scripting (XSS), distributed denial of service (DDoS), and SQL injection attacks.

Safeguarding at Layer 7 instead of Layers 3 and 4

In the realm of firewall protection, a fundamental technical distinction arises from the security layer on which these firewalls operate.

The Open Systems Interconnection (OSI) model serves as a framework that identifies and standardizes communication functions across telecommunication and computing systems.

Open Systems Interconnection (OSI) model

Web Application Firewalls (WAFs) offer protection against intrusions at Layer 7 of the OSI model, known as the application layer. This encompasses defending against various threats such as cookie manipulation, SQL injection, URL attacks, and assaults targeting application-specific technologies like Ajax, ActiveX, and JavaScript.

WAFs also focus on safeguarding the web application protocols, namely HTTP and HTTPS, which establish connections between web browsers and web servers.

For instance, in a Layer 7 DDoS attack, a flood of traffic is directed at the server layer, where web pages are generated and delivered in response to HTTP requests.

To mitigate such attacks, a WAF acts as a reverse proxy, shielding the targeted server from malicious traffic and employing filtering mechanisms to identify DDoS tools.

In contrast, network firewalls rely on Layers 3 and 4 of the OSI model to provide protection for data transfer and network traffic. This includes defending against attacks targeting protocols like DNS, FTP, SMTP, SSH, and Telnet.

Noteworthy providers such as Amazon Web Services (AWS) and Cloudflare offer Web Application Firewall (WAF) services to enhance security measures.

Comparing AWS and Cloudflare WAF: Features and Pricing

AWS Web Application Firewall

AWS WAF is a web application firewall offered by AWS, a globally recognized leader in cloud services. It is specifically designed to secure websites against web application attacks, emphasizing the protection of the application layer (Layer 7) in the OSI reference model. AWS WAF provides the following notable features:

1. Cost-effectiveness

While other WAF solutions may entail substantial upfront costs, AWS WAF has no initial charges and incurs an ongoing expense of approximately $20 per month, making it highly affordable.

2. Simple deployment

Even with a basic understanding of security, AWS WAF can be easily configured with just a few clicks. For users lacking in-depth security expertise, “Managed Rules” for AWS WAF are available, offering pre-defined defensive rules provided by security-focused vendors in the AWS marketplace. These “managed rules” are also highly cost-effective.


Cloudflare, Inc. provides a Content Delivery Network (CDN) service known as Cloudflare. A CDN is a service that globally caches (temporarily stores) images and text displayed by web applications.

Let’s explore the advantages of using Cloudflare.

1. Affordability

Cloudflare offers four different plans: Free, Pro, Business, and Enterprise. While the free plan has limited features, it allows you to get started at no cost.

The Pro plan is priced at approximately $20 per month, and the Business plan costs $200 per month, making it quite affordable.

Get the Cloudflare Business Plan for only RM900 per month. View the plans now.

2. Customization options

Depending on your plan, Cloudflare offers WAF (Web Application Firewall) and load balancing services. The WAF provided by Cloudflare may have fewer configuration options compared to AWS WAF, but it still provides a level of security against certain types of attacks.

3. Range of services

While AWS WAF focuses specifically on web application firewalls, Cloudflare serves as a Content Delivery Network. Depending on the selected plan, Cloudflare offers WAF features in addition to its CDN services.

4. Quick installation

AWS WAF can be deployed within minutes. Similarly, Cloudflare requires minimal setup, where you only need to prepare a domain name, and you can be up and running within minutes to a few days.

5. Flexibility

AWS WAF can be customized independently in various ways, and it can be combined with other AWS services like AWS CloudFront and AWS Shield for additional functionality. With higher-tier plans, Cloudflare offers additional options and features. However, it may not provide the same level of customization as AWS WAF.

6. Protection against security attacks

AWS WAF primarily focuses on preventing application layer attacks. By combining AWS Shield and other services, you can obtain further protection against DDoS and other types of attacks.

Cloudflare, on the other hand, offers defense against DDoS attacks and provides additional WAF functions to protect against application-layer attacks.

In conclusion

A Web Application Firewall (WAF) is an essential security measure for organizations with an online presence. It acts as a safeguard, protecting sensitive data and preventing malicious attacks by acting as a barrier between web applications and cyber threats. With the increasing prevalence of web-based attacks, implementing a WAF is crucial.

Moreover, newer technologies like Runtime Application Self-Protection (RASP) offer advanced protection by detecting and preventing intrusions within the application itself. By incorporating a WAF and other security measures, businesses can ensure the security and reliability of their web applications for users.

Related articles:

WAF vs. Firewall – Comparing Application & Network

A Complete Guide to Firewalls for Small Businesses

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