What Is A WAF Firewall? – What You Need to Know

A WAF firewall is an essential tool for defending your website from malicious activity. A WAF firewall is a way of protecting the data on your server and blocking any unauthorized access to it. It can also stop bad bots, hackers, and other harmful attacks that might come in through network ports or URLs. This blog post will discuss what a WAF Firewall is, how it works, and why it’s needed for you!

What Is A WAF Firewall?

A WAF Firewall is a web application firewall that can be implemented using software or hardware. It works by analyzing network traffic and looking for patterns in the way hackers try to access your website’s data through various attack vectors (SQL injection, cross-site scripting, etc.). If it finds any unauthorized activity coming from outside sources towards your website servers, it will block them immediately.

What Does A WAF Firewall Do?

A WAF firewall works as a way of securing your website from unauthorized activity. It can block different types of attacks, such as SQL injection and cross-site scripting. When you have the software installed on your web server, usually done through cPanel), it will monitor all incoming traffic and detect patterns in attack vectors that could compromise data security. This includes things like:

  • Common file uploads
  • Uncommon outgoing emails
  • Outbound requests to nonstandard ports or URLs
  • Attempts to access hidden files on the webserver
  • Use of specific functions in a programming language (like PHP) that could be used as an attack vector

Benefits Of Having A WAF Firewall Installed On A Website Or Network

  • Protection against SQL injections, malware, spambots, and other cyber attacks.
  • Improve SEO by reducing user wait times for page loading because of bad bot traffic.
  • Secure sensitive data on web servers from unauthorized access or theft.
  • Minimize downtime caused by DDoS attacks.
  • Prevent hackers from using brute force login attempts to crack passwords and get access to user accounts.
  • Protect websites against bad bots like Google scrapers (which can cause your website’s SEO ranking to drop).
  • Block users with a history of abuse or spamming activity on different forums, blogs, etc., which will improve traffic quality and conversion rates for eCommerce shopping carts.
  • Improve customer experience through faster page load times due to more minor unnecessary requests from search engine crawlers (like Bing/Googlebot) that don’t add value in conversions or usability.

How To Choose A WAF Firewall?

When you’re looking for a WAF firewall to install on your website or network, you must find one that will have the right balance of protection and usability. Many firewalls are too harsh and block out legitimate search engine crawlers from indexing your web pages, which leads to lower SEO rankings. It can also be difficult for users who visit your site regularly because they might not get access when they log in or add something to their shopping cart. When choosing a WAF Firewall, look at features like:

  • Ease of use
  • Flexibility (how easy is it to add new security rules?)
  • Ability to allow specific traffic through while blocking others based on IP address range
  • Performance (how fast does it respond to requests?);
  • Security features like anti-evasion, CRS/GRA, and DDoS mitigation
  • Ability to add custom security rules or filter traffic based on file type. You can also look at reviews from other users who have used different WAF firewalls before choosing one that fits your needs best.

How to Install WAF Firewall?

You will need to contact your web hosting provider or network administrator if you want them to install it for you. If you do decide to go through with the installation yourself, then there are some things that you’ll need:

  • Operating system (usually an Ubuntu 14.04 server)
  • Firewall software like ModSecurity
  • SSL Certificate required for it to work correctly

A basic level of Linux Command Line knowledge is recommended to set up rules, and other settings aren’t too tricky when configuring your WAF firewall on a Linux operating system. At a minimum, I would recommend having cPanel installed because most firewalls will be compatible with this control panel app by default, making installation much more accessible since many users already have it installed on their systems.

Popular WAF Firewalls


ModSecurity is an open-source web application firewall (WAF) module for the Apache and NGINX web server. It sits inside your webserver process and acts as a reverse proxy that evaluates all requests that come in through your website before they hit the leading site

It’s designed to be very flexible so that you can add security rules based on IP address ranges, file types like PDFs or executables, apps such as WordPress or Joomla! (which might tell users if their username/password combo isn’t correct), etc. 

You can also use ModSecurity to detect attacks against known vulnerabilities found in other popular CMS systems like Drupal, Magento eCommerce platforms, etc. However, it won’t prevent your site from getting hacked if you don’t fix the vulnerability.

ModSecurity is an open-source solution that makes it accessible. It also means fewer resources are available for support or documentation since not many developers work on it full-time. ModSecurity has been around since 2002 and is currently being maintained by Breach Security LLC, originally started at SpiderLabs (a division of Trustwave).


OWASP’s X-WAF is a free alternative to ModSecurity that works with the Apache webserver. It was developed by OWASP (the Open Web Application Security Project) and launched in 2015. However, it hasn’t been updated much since then, so there are no accurate statistics on how many websites currently use this firewall/intrusion detection system.

It does come included with an easy installer script that helps make installation faster for admins who don’t want to spend time configuring every bit of detail manually. This WAF also comes with some basic rules out of the box, like blocking SQL injection attempts or common exploit attacks against CMS systems like WordPress plugins being exploited using known security vulnerabilities found online.


The third WAF firewall that I’m going to recommend is Incapsula. They offer a cloud-based intrusion detection system (IDS) and their web application firewall solution. Their main selling point over the other two solutions mentioned above is that it’s not open source and comes with additional security features like DDoS protection, anti-evasion capabilities, etc., but at the cost of having to pay every month unless you want your IDS/WAF disabled completely. 

They do have a free trial, though, so if you’re interested in giving them a shot, then check out their site or sign up here:  https://www.imperva.com/products/web-application-firewall-waf/


Once it detects any unauthorized activity coming from outside sources, it will block those requests and prevent them from accessing your website data or doing anything harmful. It’s essential for all websites with user accounts, eCommerce shopping carts, etc., to have this type of protection because hackers can often gain access through vulnerabilities like SQL injection attacks by tricking your database into running their code on the system. A WAF firewall works to close these gaps so attackers can’t get at your data.

While ModSecurity, OWASP’s X-WAF, and Incapsula are the top three WAFs out there for securing your websites against hackers looking to exploit vulnerabilities found in popular CMS systems like WordPress or Joomla! You can also check out other similar solutions made by companies like Barracuda Networks (very expensive), Cloudflare (useful if you’re already using their CDN service), or Trustwave (more costly than both of the previous options). 

Other free alternatives include Naxsi, an open-source web application firewall designed for use with NGINX servers; Sqreen, another cloud solution that focuses on security monitoring instead of intrusion prevention.

Common Questions and Troubleshooting Solutions

Q: I’m worried about the performance impact of running a WAF firewall on my website. Should it slow down page load times?

A: If your web server is configured correctly and you don’t have any issues with memory or CPU usage, there should be no noticeable effect. However, if you find that ModSecurity slows down the site too much, OWASP’s X-WAF could provide better results since its footprint is smaller than what comes bundled with ModSecurity. And finally, Incapsula claims to perform well even when protecting many websites from attacks coming in simultaneously, so as long as your provider can handle high traffic volumes, then this shouldn’t end up being an issue either.

Q: Do I need to run both a WAF firewall and an IDS/IPS?

A: No, WAF firewalls are only meant to stop attacks in progress, while intrusion detection systems offer protection before any sort of hacking attempt is made, so you should run both types on the same system. 

Q: I’m worried about false positives when it comes to blocking malicious traffic. Can my website still get hacked if something gets blocked by mistake?

A: False positives shouldn’t happen too often since most rulesets have been designed based on real-world hacker activity, but there’s always a tiny chance that this might take place. Keep in mind, though, that even if your site does end up getting compromised by hackers, then they won’t be able to do much with it unless they’ve found a vulnerability in your CMS system, so running an IDS or IPS will still help to stop hackers from exploiting known security issues before they can do any damage.

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