Web Application Firewall (WAF): Definition and Its Functions

Web Application Firewall (WAF) is one of the important tools that can be used to secure websites. The use of WAF will strengthen the existing data security system on the web so that it is not vulnerable to misuse.

Now more and more businesses that provide their products or services on the internet are adopting this technology as an effective solution to balance performance, guarantee network security, and of course more cost-effective.

Basically, the main task of WAF is to protect specific applications from the threat of web-based attacks in the application layer. However, WAF is now growing with more sophisticated features, such as load balancing, intrusion prevention, and threat intelligence.

In addition, in terms of WAF technology is also increasing and becoming part of more comprehensive security solutions such as Next-Generation Firewall (NGFW), Unified Threat Management (UTM) and many more.

Table of Contents

What is a Web Application Firewall (WAF)?

what is Web Application Firewall

Before discussing in more detail about the Web Application Firewall, it’s good if you first know the concept of a Firewall. In short, a firewall is an application concept whose main function is to block, monitor, and filter data. As a security system, a firewall can prevent access to networks whose data is considered unauthorized.

Meanwhile, Web application firewall is a technology that functions for blocking, monitoring, and filtering data. This means that before entering a website or web application, the client data will be checked first by the WAF.

On a network, WAF will analyze client data as well as detect malicious traffic. The traffic in question is access that has the potential to damage the website. Therefore, WAF is often used as a security system to protect websites from various threats such as malware, exploits, to viruses.

WAF itself is a firewall application that is usually used for Hypertext Transfer Protocol (HTTP) applications. In a website service, WAF acts as a gatekeeper who monitors all forms of traffic. This WAF implementation prevents cyber crimes such as SQL injection, XSS, DDoS, cross-site forgery, and others.

Web Application Firewall is a form of layer 7 protocol protection and is not designed to protect against all types of cyber attacks. This mitigation method is usually a set of tools that creates comprehensive protection against a series of attack vectors.

In this way, this technology can quickly detect and secure websites from the most dangerous attacks, which traditional firewalls such as IDSes and IPSes are unable to do.

Types of WAF

type of WAF

After knowing about the definition of a Web Application Firewall, you also need to know about the types of WAF. Based on the technology, WAF or Web Application Firewall has three different base types.

For your information, here are some types of WAF that you need to know:

1. Network Based Web Application Firewall

One type of WAF that you need to know about is Network-Based WAF. This type of WAF is based entirely on hardware aka hardware and can reduce latency because it is installed locally and near applications.

Read: Peer to Peer Networks: Complete Introduction

Many hardware-based WAF solution providers enable replication rules across their devices, which allows users to deploy and configure at scale. The drawback of this type of WAF is a matter of cost, because the business will be asked for a down payment and operational maintenance costs.

2. Cloud-Based WAF

The next type of WAF you need to know is Cloud-Based WAF. Cloud based WAF is easier to implement because to divert traffic it only requires a simple domain system or proxy change. To be able to use cloud-based WAF you have to work with a third party. Therefore, make sure you choose a reliable and trusted WAF service provider.

Even if you have to entrust your company’s traffic to a third party such as a WAF solution provider, this step is guaranteed to protect your application across a wide spectrum of hosting locations. Not only that, the WAF solution provider must also have the latest security system updates and can identify the most recent threats.

3. Host-Based WAF

Host based WAF is the most customizable type and is fully integrated into the application code. Even so, the use of host-based WAF can also be more difficult because it still relies on local servers. In order to be able to manage WAF optimally, at least you need an additional team such as system analysts, developers, and DevOps.

That’s the division of the types of Web Application Firewall (WAF) that you need to know. Each type of WAF certainly has its own functions and advantages. Therefore, make sure you choose the type of WAF that is most appropriate and suits your needs.

How WAF Works

how does WAF works

Although it sounds simple, WAF actually has a fairly complex concept. Broadly speaking, the way WAF works is to analyze HTTP requests and apply a number of predetermined rules. This is done to determine which parts of HTTP are eligible or suspect.

In general, there are two main parts of HTTP that WAF targets, namely GET and POST. GET is the part used to retrieve data on the server. While POST is part of HTTP which is used to send data to the server.

Read: What is a Hub: Definition, Types, and How They Work

WAF has 3 ways to analyze and filter HTTP, namely whitelisting, blacklisting, and hybrid security. For information, the following is an explanation of the method used by WAF for HTTP filtering:

1. Whitelisting

The first method used by WAF to filter HTTP is through the whitelisting method. At this stage, WAF will reject all requests by default and only allow requests that have been trusted.

This method is somewhat easier than blacklisting, but you have to be careful because errors in granting permissions can cause traffic blocking accidentally. Make sure you only allow IP addresses that are known and trusted to reduce the risk of data theft.

2. Blacklisting

The next method used by the Web Application Firewall (WAF) to filter HTTP is through Blacklisting. The blacklisting method is usually done to block traffic that is considered dangerous from a website or web application.

In this method WAF will apply certain presets and release data by default. Blacklisting is very suitable when there is a lot of unknown IP traffic, for example public websites.

This method is considered more suitable for public websites because a lot of traffic gets from unknown IP addresses. However, blacklisting has drawbacks where it requires more effort to use, and must have more information to filter data based on detailed information.

3. Hybrid Security

The next method also used by WAF for HTTP filtering is Hybrid Security. This method is a combination of Whitelisting and Blacklisting so that it allows you to use both methods simultaneously.

Benefits of Using a Web Application Firewall (WAF)

benefit of WAF usage

After knowing what a Web Application Firewall (WAF) is, you also need to know the benefits of the WAF. WAF offers a number of benefits over other traditional firewalls, as it has better visibility into sensitive data from the HTTP layer. WAF can prevent application layer attacks that would normally bypass traditional firewalls.

As an added explanation, here are some of the benefits of WAF that you need to know about:

1. Prevent Cross-Site Scripting Attacks

One of the benefits that can be obtained from using WAF is to prevent Cross-Site Scripting (XSS) attacks. In short, XSS is a web security breach that allows attackers to insert malicious scripts. Impersonating a user and directly accessing important information are examples of XSS attacks.

2. Preventing SQL Injection

The next benefit that can be obtained from the use of WAF is to prevent SQL injection. In short, SQL injection is the exploitation of database vulnerabilities in executing queries. In this case, it allows attackers to create and modify user permissions, thereby destroying sensitive data.

3. Preventing DDoS Attacks

The next benefit that can be obtained from using WAF is to prevent DDoS Attacks from occurring. In a DDoS attack, the attacker’s target is to overload the server and its infrastructure with traffic attacks. The server continues to experience slowdowns until it is finally unable to process incoming requests from legitimate users.

4. Prevent Malware Attacks

The use of a Web Application Firewall (WAF) can also be used to prevent Malware attacks on sites. Malware is software that is usually used by hackers to exploit and damage networks, servers, and devices.


WAF is one of the important components that can be used to protect the data security of a website. The use of WAF will ensure that the data on the website server will not be easily accessed by irresponsible people.

In short, WAF is a technology that functions for blocking, monitoring, and filtering data. WAF technology has three different methods for securing data on websites, namely Whitelisting, Blacklisting, and also Hybrid security.

That’s a complete discussion of what a Web Application Firewall (WAF) is that you need to know. After reading the article, hopefully you can have a more detailed and complete understanding of WAF and its benefits.

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