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What Is A Web Application Firewall? WAF Explained

Jao Gavino
May 25, 2024


Today’s Internet has become quite a scary place. Just last year, there was an overall year-on-year increase of 74% in the number of distributed denial-of-service (DDoS) attacks across the world (according to StormWall’s DDoS Year-in-Review). Yikes!


This is a very worrying number, especially if you’ve just created your website. Spending all that time setting up and building a beautiful website doesn’t amount to much if your site is constantly brought down by DDoS attacks!


Fortunately, this is where web application firewalls (WAFs) come in—these sophisticated web security systems have become an essential part of any business’s cybersecurity suite. A WAF will protect you not only from DDoS attacks but also from other types of cyberattacks.


Sounds great, right? If you’re wondering how this powerful system works and protects your website from online attackers, the different types of WAF, and how to set one up for your site, read on!



What Is A Web Application Firewall (WAF)?


web application firewall waf

Your WAF acts as a barrier against DDoS, SQL injections, and other cyberattacks. (Source: Network World)


A web application firewall is a software- or hardware-based solution that monitors and protects websites from malicious traffic. It’s designed to protect from various attacks, such as DDoS attacks, SQL injections, or cross-site scripting (XSS).


How does a WAF Work?


Simply put, a WAF acts as a barrier (hence the wall part of its name) that prevents unsanctioned entry (and exit) from a network. Imagine a castle: its walls prevent any invaders or thieves from entering, and the king (or whoever owns the castle) only allows specific individuals to enter—that’s pretty much what a firewall is.


In a more technical sense, a WAF works by inspecting all HTTP/S traffic traveling to your web application and then filtering and blocking any traffic that is deemed to be malicious. Plus, it also prevents any unauthorized data from leaving the app.


It does all this by following a set of policies that helps ascertain what traffic is malicious and what traffic is safe. You can customize these policies to meet your application’s unique needs as well as update them to address any new vulnerabilities, just like you’d do with your antivirus software.



Why Do You Need A WAF?


As we’ve stated, WAFs exist to protect you from different attacks by monitoring incoming HTTP requests, analyzing them for any malicious behavior, and then blocking suspicious activity before it even reaches your web servers.


This means that instead of waiting for an attack to happen — which could take hours or even days — you can identify threats early on in their life cycle and shut them down before they cause damage or cost you money in terms of lost productivity or brand reputation damage.


This ensures that your website stays up and running for its users as well as guarantees the safety and privacy of their data. After all, a website with a happy user base is a successful website!



What Are The Different Types Of WAF?


types of waf

Although there are different types of WAFs, all of them work by preventing malicious traffic from accessing your server. (Source: Cloudflare)


Now that you have an idea of what web application firewalls are, let’s talk about the different types of WAFs:


  1. Network-based WAFsNetwork-based WAFs are typically hardware-based solutions that are installed locally, which helps minimize latency. However, network-based WAFs are the most expensive type of WAF, requiring you to store and maintain physical hardware.
  2. Host-based WAFsOn the other hand, host-based WAFs are software-based solutions that can be fully integrated into an application. These WAFs are cheaper than network-based ones and are also more customizable.
    The downside to host-based WAFs is that they consume local server resources, are quite difficult to implement, and are costly to maintain.
  3. Cloud-based WAFsFinally, cloud-based WAFs are highly affordable and easy-to-implement solutions that involve paying a monthly or annual fee to a third party to utilize their WAF. This WAF is regularly updated for free, saving you the time and effort usually required to manually update a WAF configuration.
    The main disadvantage to cloud-based WAFs is that because you’re relying on a third party, you’re going to have to sift through a lot of options to find a WAF with a formidable set of features and enough customizability to meet your organization’s needs.



How About The Different WAF Security Models?


Next, we’re going to be taking a look at the three security models for WAFs:


1. Positive security model


positive security model

A positive security model only allows those on your whitelist to access your site—no hackers allowed!


A positive security model utilizes an allowlist or whitelist to filter traffic. Simply put, only the types of traffic specific to this list will be allowed; everything that isn’t on the list is outright blocked.


The main advantage of this security model is that it can easily block new or unknown types of attacks, as the traffic that is allowed is highly regulated via the allowlist.


Imagine an invite-only party: only those with an invitation are allowed, and those without one are prevented from entering. That’s basically how a positive security model for your WAF works.


2. Negative security model


negative security model

In a negative security model, anything on your blacklist is denied access, locking away any would-be attackers from your site!


Conversely, a negative security model utilizes a denylist or blacklist to filter traffic. Anything on this list is immediately blocked, and everything that isn’t on the list is given access.


The main advantage of this security model is that it is much easier to implement since you’ll only be filtering traffic that is known to be malicious.


However, the main downside to this model is that it cannot block all threats, especially newer ones. It also requires you to maintain a running list of malicious signatures, which can rapidly grow with each new threat.


All in all, a negative security model’s level of security depends entirely on the number of blacklisted items. Staying on top of new threats (and then adding them to your blacklist) is of paramount importance when using a negative security model.


3. Hybrid security model


Fortunately, many WAFs offer a hybrid security model, which implements both models, allowing you to capitalize on their advantages while also minimizing their downsides.



5 Important Reasons Why You Need A WAF


why waf is needed

Properly utilizing a WAF ensures your site’s compliance with various standards and regulations, such as HIPAA and PCI DSS. (Source: Florida DOEA)


Now, let’s discuss 5 important reasons why you’d need a WAF:


  1. It helps prevent a wide variety of attacks. A WAF monitors and filters the traffic that goes to your website, blocking DDoS attacks, SQL injections, XSS, cross-site forgery, and local file inclusion, among others.
  2. It prevents hackers from compromising your customers’ data. Taking care of your customers (and their precious data) earns their trust, ensuring their safety and your site’s longevity and success.
  3. It also helps free up your resources. Instead of constantly monitoring your traffic and manually blocking attacks, you or your team can simply set up a WAF and then work on something else!
  4. A WAF also ensures compliance with various regulations, such as the Health Insurance Portability and Accountability Act (HIPAA) or the Payment Card Industry Data Security Standard (PCI DSS) to comply the PCI compliance.



How To Set Up A WAF On Your Website


With all of these benefits, you may now be wondering how you’d go about setting up a WAF for your website. Don’t worry! We’ve got you covered—here are three ways to get a firewall up and running for your website:


1. Via your web host


Hostinger homepage

Hostinger is one provider that offers a WAF with its plans.


This is where being picky with your hosting service comes in handy—the best web hosts offer a WAF as part of the security features for specific packages. For example, Hostinger offers its own WAF with its Premium ($2.99/mo) and Business ($3.99/mo) hosting services.


2. Via WordPress plugins


wordfence security

Wordfence is a plugin that offers a WAF in addition to a variety of other security features.


Alternatively, if you’re looking to secure your WordPress site, you can simply install a security plugin that has a built-in WAF.


For example, Wordfence Security offers a WAF that blocks malicious traffic and is automatically updated. What’s more, it also offers malware scanning, two-factor authentication, and an easy-to-use dashboard—all for free.


For $119 per year, you can get Wordfence’s premium version, which includes additional benefits, such as premium customer support, real-time firewall rules, country blocking, and a dynamically updated blocklist of malicious IPs.


If Wordfence just isn’t cutting it for you, we got you covered—here’s our list of the best WordPress security plugins, where you can easily compare various options and their prices!


3. Via a third party


cloudflare logo

Cloudflare’s WAF offers a large selection of features that helps it stand out from other third-party offerings.


And last but certainly not least, you can also sign up with a third party to utilize their WAF services. As an example, let’s take a look at Cloudflare’s WAF:


It’s very easy to set up, with Cloudflare stating that their WAF can be set up “with just a few simple clicks,” even for untrained users.


It lets you set custom rules, allowing you to manually configure Cloudflare’s WAF to protect against certain threats or implement policies that are specific to your organization.


It has multiple highly customizable security features, such as the following:


  • Cloudflare-managed rules that defend against zero-day vulnerabilities
  • WAF machine learning to protect your site against XSS, SQL injection, and remote code execution
  • Exposed credential checks that monitor and block the use of stolen credentials to take over accounts
  • Advanced rate limiting that protects against DDoS attacks and brute-force attacks
  • Alerts regarding responses that contain sensitive data


To get these features, you won’t even have to break the bank: Cloudflare’s plans start at $20 per month for the Pro option, going up to $200 per month for the more advanced Business option.



A (Fire)Wall To Defend Against Threats


As you can see, having a WAF can do wonders for your site’s security—and it doesn’t even require that much technical knowledge to set up! Like its namesake, it’ll act as a barrier that protects you from numerous threats and attacks.


With our tips and recommendations, you’re now more than ready to get a WAF up and running for your very own website—and reap all of the benefits that it brings.