Top 11 Best Web Application Firewalls

Whether it’s your online business, blog, or any website, if it isn’t safe, people won’t be able to visit. Search engines won’t provide a link to it. 

This will negatively affect your business as you would lose valuable customers. 

Thus, you must keep your webpage and website safe from hackers who might inject a virus, malware, or other adware into it.

Web Application Firewall (WAF) is one such software that will help you achieve it.

What is a WAF? | Web Application Firewall (WAF) explained

WAF are firewalls for web applications and websites to protect them from being vulnerable to hackers.

They are the most common security measure used by various enterprises to protect their web-based applications against impersonation, cross-site forgery, file inclusion, malware infections, zero-day exploits, SQL injections, cross-site scripting (XSS), and other threats and vulnerabilities.

The firewalls monitor, filter, and then block harmful data packets when they travel to and from the website.

WAF can run via network appliance, cloud-based service, or server plugin to inspect each data packet and analyze layer 7- application (OSI model) logic based on some rule. 

It is often deployed through a reverse proxy. It is placed in front of websites or applications to filter out potentially dangerous traffic that may violate and exploit your web applications.

If your enterprise owns an e-commerce platform, online banking platform, or other platforms with frequent interaction between customers and your business, WAF is a must for you.

Traditional network firewalls and other intrusion detection and prevention systems (IDS and IPS) may not be capable of immediately detecting and preventing most dangerous vulnerabilities, but WAF can.

WAF allows frequent policy modification with ease to facilitate a faster response against various attack vectors. For example, during a DDoS attack, rate limiting may be implemented quickly by modifying WAF policies.

How does application firewalls or WAFs work?

WAF analyzes the HTTP (Hypertext Transfer Protocol) requests such as GET and POST and applies a set of security rules to define the benign and the malicious parts.

  • GET is an HTTP request that is used to retrieve data from the server.
  • POST is an HTTP request that is used to send data to the server for the state change.

Just as a proxy server is an intermediary to save a client’s identity, WAF acts as a reverse proxy acting as an intermediary protecting applications servers from malicious clients.

Types of Web Application Firewalls

There are broadly three types of Web Application Firewalls (WAF):

1. Host-based WAF

This type of firewall is fully integrated into the applications code that allows lower cost and higher customization options.

However, these WAFs are challenging to maintain as they require application libraries and are highly dependent on the local servers’ efficiency.

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Host-based WAF requires system analysts, developers, and DevOps/DevSecOps as staff resources.

2. Network-based WAF

These WAFs are hardware-based that are installed locally on-premises using a dedicated appliance that is close to the application. It helps in reducing latency.

Network-based WAFs are costly as they require capital hardware resources expenditure, hardware maintenance and other operational costs.

With replication of a set of rules for security and settings across various appliances, large-scale deployment, maintenance, and configuration are possible.

3. Cloud hosted WAF

These WAFs are low-cost solutions that require minimal resources to implement and manage by the organizations.

Cloud WAFs are third-party entities which makes it difficult for organizations to trust them with their data.

However, these entities allow a broad spectrum of hosting locations, protection against application-layer attacks, and help identify and block the new threat using their latest intelligence.

These firewalls come with easy deployment on a subscription basis and offer a simple DNS (Domain Name Server) or proxy to redirect traffic.

Difference: A web application firewall (WAF), an intrusion prevention system (IPS), and a next-generation firewall (NGFW)

Web Application Firewall (WAF)

It is used to protect the application layer from malicious attacks aimed at the application layer by analyzing HTTP/s requests.

WAFs ensure that only allowed actions at the application layer are performed by being aware of the user, session, and application behind the web applications and their services.

The organizations trust them because they can listen and analyze all the communications before they reach the end-user.

Intrusion Prevention System (IPS)

It is a broadly focused product typically used for well-known owasp vulnerabilities and attack vectors by analyzing signature databases and every policy.

IPS standards are defined using the signature database and policies, and if any traffic deviates from these standards, then an alarm or alert is sent.

DNS, TELNET, FTP, SSH, SMTP, etc., are a few protocols used by IPS to protect OSI layers 3 and 4.

Next-generation Firewalls (NGFW)

It monitors traffic across websites, SaaS, and email accounts to protect web users by enforcing user-based policies.

Features such as anti-virus, anti-malware, personal Intrusion Prevention System (IPS), and URL filtering add context to the web application security policies of NGFW.

What is the difference between blocklist and allowlist WAFs?

Blocklist WAF – A WAF can operate on a blocklist, i.e., a negative web application security model, by protecting against known attacks. You may imagine it as a security personnel that denies entry to anyone who does not comply with the restaurant’s policies.

Allowlist WAF – A WAF can operate on an allowlist, i.e., positive web application security model, by allowing access to only pre-approved data movement. You may imagine it as an exclusive restaurant security personnel that helps only the ones with a prior reservation.

What Attacks do WAFs protect against?

Numerous attacks are happening all over the internet every day. Application firewalls provide security to the webserver from the following attack categories:

Web Scraping: Attackers can automate the data extraction from web pages.

Third-party misconfigurations: Content inserts provided by other companies are manipulated.

Layer 7 DoS attack: It happens when the web server receives overwhelming recursive requests for the application.

Site vulnerabilities (SQL Injections – OWASP): Queries that are entered in user authentication fields can be exploited.

Cross-Site Scripting (XSS): Hackers can insert malicious HTML code into the web page.

Cookie poisoning: The parameter values held in cookies passed between web pages can be corrupted with alternate values.

Backdoor or Debug options: Hackers can exploit the developer feedback options available on the web page for testing to access the processor.

Forced Browsing: Hackers can get access to temporary and backup folders on the web server.

Stealth commanding: It is an attack on the web server’s operating system.

Buffer overflow: Attackers use the input to overwrite the code stored in memory.

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Parameter tampering: hackers can alter the parameter values that are used for a web page call.

WAF covers the front end of a website, due to which several essential access control functions are not provided.

It focuses on HTTP and other requests such as FTP. It also covers HTTPS and SFTP.

Choosing a Web Application Firewall (WAF) solution

You should have now understood that a WAF is a must for your organization and your application or website’s security.

You must choose the best WAF solution. You have multiple services available that provide WAF on the network or as cloud-based. All these options make choosing the right web application firewalls time-consuming.

Here we have a few suggestions that will help you choose the best WAF for you.

  • Narrow down what you want from the WAF and find the retailer that best suits your needs.
  • Choose the correct services, software, and equipment suitable to your needs.
  • Consider the capacity and scalability factors while deciding the service. It will help you with future expansion plans.
  • Decide between dedicated hardware-based or cloud-based WAF.

11 Best Application Firewalls for 2021

Here we have a list of the top 11 WAFs in the market in 2021 to help you protect your application and website from attack.

1. Sucuri Website Firewall

Sucuri is a Web Application Firewall Application

Sucuri is a cloud-based protection system that is a part of a website protection suite. For using this, you need to host your website on Sucuri’s server so that all the web traffic can be routed through it and monitored.

Sucuri maintains an attack signature database that is continuously updated and can help your application get enhanced and updated security measures while Sucuri provides security to other websites.

Your website’s delivery performance will be enhanced by using cache by which, even if your website is down for maintenance, webpages can still be accessed by customers.

2. Prophaze WAF-As-A-Service

Prophaze WAF-As-A-Service is a Web Application Firewall Application

Prophaze is a cloud-based proxy server that includes AI routines to refine detection rules and adjusting standard baseline behavior to reduce false alarms. 

This system operates itself with Kubernetes containers to monitor the performance and security of the system’s Kubernetes and potential hacker detection activities.

Prophaze WAF is relatively simple to use as it is aimed at small businesses and does not require high technical know-how.

3. Akami Kona Site Defender

Akamai Kona Site Defender is a Web Application Firewall Application

Akami gives full DDoS protection using a cloud service firewall called Site Defender. It is the world leader in DDoS mitigation.

This helps combine the benefits of both the security services in one, thereby eliminating the need to route the data movement via two different companies to get genuine requests.

4. Fortinet FortiWeb

Fortinet Fortiweb is a Web Application Firewall Application

This SaaS system is a VM-based software package or appliance that examines all traffic moving through the network and uses an AI-based machine learning approach to detect suspicious activity on the network.

FortiWeb, an Application firewall, is also available for private clouds and can be implemented using a container-based system.

It allows DDoS protection service and uses threat intelligence feed to provide better security and analyze patterns in deviating behavior that seems to lead towards an attack.

5. MS Azure Web Application Firewall

MS Azure Web Application Firewall is a Web Application Firewall Application

MS Azure WAF is a world-renowned hypervisor system available on AWS, one of the most successful cloud platforms.

It acts as a proxy to inspect and block suspicious traffic inbound to your application. It also examines outbound traffic for any possible data loss events. The system can automatically track OWASP top 10 common vulnerabilities. 

Azure does not charge its users by subscription but by a metered charge rate calculated using an hourly rate and data throughput rate.

5. Imperva Cloud WAF

Imperva Cloud WAF is a Web Application Firewall Application

This primary cybersecurity provider has comprehensive WAF services. Similar to other application firewalls, Imperva Cloud WAFs online version also acts as a proxy.

The service comes with other web enhancement services like content delivery network (CDN) to speed up web page delivery and provide constant availability in primary server failure.

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It also comes with a virtual patching service and managed service option for cloud WAF.

7. AppTrana Managed Web Application Firewall

AppTrana  is a Web Application Firewall Application

AppTrana is one of the best web firewalls from Indusface that provides a fully managed firewall with content acceleration and CDN.

It comes with core managed rule sets which are optimized to provide instant blocking. The rule sets were made after assessing the security of thousands of websites.

Customers are allowed for an on-demand security assessment to gain instant visibility on their WAFs and its rules.

Customers request specific rules from a centralized portal and from the 24*7 MSS team to create Zero WAF false-positive assurance regulations.

8. F5 Essential App Protect

F5  is a Web Application Firewall Application

F5, which owns NGINX Inc., is an established cybersecurity provider that adapted F5 Application Security Manager (pre-existing WAF for network appliances) to create F5 Essential App Protect.

The F5 Application Security manager is now called the BIG-IP Advanced WAF and still exists alongside F5 Essential App Protect.

The App Protect WAFs are easy to set up and are designed for use by non-technical users through a dashboard via any browser.

9. Cloudflare WAF

CloudFlare is a Web Application Firewall Application

Cloudflare is one of the most successful DDoS attack protection web application firewall. It is a widely used service with more than 2.9 million requests per second due to a large customer base.

Since this is a widely used cloud service, every customer defect is blacklisted, which can significantly help your business. 

10. Barracuda Web Application Firewall

Barracuda is a Web Application Firewall Application

Barracuda WAF is available as SaaS, virtual appliance, appliance, or private cloud installation to allow implementation flexibility for businesses of various sizes.

It monitors all the inbound and outbound traffic and can block traffic-based attacks, on-page attacks, and malware using blacklisting and whitelisting.

Barracuda also provides prevention from data loss to enable businesses to comply with data protection standards.

11. StackPath Web Application Firewall

StackPath is a Web Application Firewall Application

StackPath is a subscription-based cloud-based service suite specializing in specific “edge technology,” which pushes the connected services to the edge and then beyond.

StackPath provides offsite configuration to provide customers with extra web server protection so that the malicious code can’t even touch your resources.

The three effective defenses that StackPath offers are browser validation, IP address assessment, and the use of content-based routing rules.


Firewall for Web applications is very important for any web-based applications and web sites.

There are numerous third-party providers that may help you in getting that extra protection you need against hackers.

Frequently Asked Questions

What is the firewall in a Web application?

It is a firewall between the users and the web applications that analyzes the HTTP requests to protect the business from potentially malicious users and code.

Do I need a Web application firewall?

Generally speaking, a Web Application Firewall (WAF) is a must for any organization that wants to protect its website and business from unwanted malicious attacks. WAF can block unwanted traffic and protect against various attacks such as SQL injection, brute-force attack, cross-site scripting, zero-day exploits, DDoS attacks, and other types of hacks.

What is the benefit of a WAF or web application firewall?

The Application Firewalls protect the web applications by inspecting and filtering traffic moving in and out of the application. It helps defend the web application against various attacks, including OWASP vulnerabilities.

What is the difference between a WAF and a firewall?

Although both are firewalls that work on the network, the fundamental difference between them is that WAF targets Hypertext Transfer Protocol (HTTP) traffic. In contrast, the firewalls are aimed at the internal and external network traffic.
Thus, web application firewalls (WAF) act as a barrier between external users and web applications, while firewalls act as a barrier between external and internal network traffic.

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