WAF (Web Application Firewall)

WAF (Web Application Firewall) is a security solution designed to protect websites, web applications, web services, and APIs from cyberattacks. Unlike traditional firewalls, which inspect network traffic at the IP address and port level, a WAF analyzes HTTP and HTTPS requests to detect malicious activity targeting web applications.

Today, WAFs are a key component of cybersecurity for online stores, corporate portals, SaaS platforms, banking services, and other web-based systems. The technology helps prevent breaches, data leaks, and service disruptions by providing an additional layer of protection between users and application servers.

According to industry research, most attacks against web applications target vulnerabilities within the application itself rather than the underlying infrastructure. For this reason, WAF deployment has become a standard security practice for modern online services.

What Is a WAF in Simple Terms?

In simple terms, a WAF can be thought of as an intelligent security filter that inspects every request sent to a website or web application before it reaches the server.

For example, when a user visits an online store and browses products, their requests pass through the WAF and are forwarded to the application without interruption.

If an attacker attempts to send a malicious request to compromise the website or steal data, the WAF detects suspicious activity and blocks it before it reaches the server. In this way, a WAF acts as an additional security barrier between the internet and a web application.

Why Is a WAF Needed?

The primary purpose of a WAF is to protect web applications from common online threats. It is used to:

• Prevent attacks against websites and APIs
• Protect user data
• Prevent unauthorized access
• Reduce the risk of data breaches
• Support security and compliance requirements
• Improve web service availability

Protection is particularly important for applications that process personal information, payment data, or sensitive business information.

How a WAF Works

A WAF sits between users and the web application. When a request is sent to a website, the following process typically occurs:

1. A user sends an HTTP or HTTPS request.
2. The request passes through the WAF.
3. The WAF analyzes the request content.
4. If no threat is detected, the request is forwarded to the server.
5. If suspicious activity is identified, the request is blocked.

Analysis can be based on various criteria, including:

• Known attack signatures
• Security rules and policies
• Anomalous behavior
• Source reputation
• Behavioral analysis

Modern WAF solutions can make decisions in near real time.

What Threats Does a WAF Block?

One of the primary functions of a WAF is protecting against attacks that are among the most common web threats.

• SQL Injection. Attackers attempt to inject malicious SQL code into database queries. A WAF can detect and block such attempts.
• Cross-Site Scripting (XSS). This attack aims to inject malicious JavaScript code into web pages. A WAF helps prevent the execution of such scripts.
• Local File Inclusion (LFI) and Remote File Inclusion (RFI). These attacks attempt to gain access to server files or execute external code.
• Command Injection. An attempt to execute system commands through application vulnerabilities.
• API Attacks. Modern web applications actively use APIs for data exchange. A WAF can monitor API requests and identify suspicious activity.
• Bots and Automated Attacks. A WAF can detect malicious bots and limit their activity.

Types of WAF

There are several ways to deploy WAF technology.

Hardware WAF

A hardware WAF is a dedicated appliance installed within an organization’s infrastructure. Advantages include:

• High performance
• Full configuration control
• On-premises deployment

This approach is commonly used by large organizations and data centers.

Software WAF

A software WAF is installed as software on a server or virtual infrastructure. Advantages include:

• Flexibility
• Lower implementation costs
• Easier integration

Cloud WAF

Cloud-based WAF solutions are the most popular option for modern web projects. Advantages include:

• Fast deployment
• Automatic updates
• Global infrastructure
• Scalability

Cloud WAF solutions are often delivered as a Security as a Service (SECaaS) offering.

WAF vs. Traditional Firewall

Although both are security technologies, they serve different purposes. A traditional firewall operates at the network level and controls:

• IP addresses
• Ports
• Network protocols
• Traffic routing

A WAF operates at the application layer and analyzes the content of web requests. As a result, these technologies complement each other rather than replace one another.

FAQ

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