What Does A Web Application Firewall Do?


What Is A Web Application Firewall?

web application firewall (WAF) is a specific form of application firewall that filters, monitors, and blocks HTTP traffic to and from a web service.

A WAF or Web Application Firewall helps protect web applications by filtering and monitoring HTTP traffic between a web application and the Internet. It typically protects web applications from attacks such as cross site forgery, cross-site-scripting XSS file inclusion, and SQL Injection among others. A WAF is a protocol layer 7  defense (in the OSL MODEL, and is not designed to defend against all types of attacks. This method of attack mitigation is usually part of a suite of tools which together create a holistic defense against a range of attack vectors.

By deploying a WAF in front of a web application, a shield is placed between the web application and the Internet. While a proxy server protects a client machine’s identity by using an intermediary, a WAF is a type of reverse proxy, protecting the server from exposure by having clients pass through the WAF before reaching the server.

A WAF operates through a set of rules often called policies. These policies aim to protect against vulnerabilities in the application by filtering out malicious traffic. The value of a WAF comes in part from the speed and ease with which policy modification can be implemented, allowing for faster response to varying attack vectors; during a DDos Attack rate limiting can be quickly implemented by modifying WAF policies.

How does application firewall work?

Web application firewall software is generally available as a web server plugin or an inline web server. Whether software or hardware, a web application firewall analyzes the GET and POST requests sent through HTTP and HTTPS, and applies configured firewall rules to identify and filter out malicious web traffic

When selecting a ‘Web Application Firewall‘ or WAF solution to protect your applications, you should prioritize the following features to achieve application security efficacy.

  1. Protection Against The OWASP Top 10OWASP or “Open Web Applications Security Project,” is an open software security community collecting, among other things, the list of top attacks against web servers.OWASP Top 10Your WAF must protect web applications and servers from the OWASP Top 10 to ensure security against the most prevalent application attacks.The effectiveness of a WAF solution’s security against the OWASP Top 10 is difficult to discern without testing. Seeking research testing and validation from a trusted organization is a reliable way to gain insight into the effectiveness of leading WAFs in the market.Consider reviewing the Security Value Map™ (SVM) and Comparative Analysis Report™ (CAR) series by NSS Labs, which evaluates leading WAF products on their ability to prevent intrusions, and detect and mitigate threats.
  2. Protection Against Known and Unknown AttacksYour WAF should support both a positive and a negative security model.A negative security model is easy to deploy because it protects against known exploits.A positive security model denies all transactions by default, but uses rules to allow only those transactions that are known to be valid and safe. This approach is more efficient (fewer rules to process per transaction) and more secure, but it requires very good understanding of the applications being protected.WAF security model
  3. PCI DSS ComplianceMalicious attacks designed to steal sensitive credit card information are increasing, with more and more security breaches and data thefts occurring daily. PCI DSS requirements have been revised in an attempt to prevent these types of attacks and keep customer data secure.If your organization works with, processes, or stores sensitive credit card information, you must comply with PCI DSS requirements. You must strengthen your security posture by protecting your critical web applications, which are often easy pathways for malicious attackers to gain access to sensitive cardholder data.While you can adhere to PCI DSS standards by deploying a vulnerability scanner or a WAF, the most effective solution is to integrate the data from scanning technology with the attack-mitigation power of a WAF.The WAF you invest in should identify, isolate, and block sophisticated attacks without impacting legitimate application transactions. In addition, your WAF should offer PCI reporting, which determines if compliance regulations are being met, and if they are not, details the steps required to become compliant.“Of all the data breaches investigated over the last ten years, not a single company has been found to be PCI compliant at the time of the breach.” –Verizon
  4. High Performance Without Negative ImpactPerformance is key when it comes to a WAF. The WAF you choose should not impact the performance of existing infrastructures, including application and network devices.This means that even though the WAF acts as the security proxy to the application, the application continues to transact the data without suffering from a backlog of requests and does not collapse under heavy loads.The application should behave as though no WAF is present. And from the end user perspective, the WAF should be completely transparent. Users should not experience any noticeable delay or hindrance of service.WAF performance
  5. Centralized ManagementCentralized management is crucial when you’re dealing with web application infrastructure that is distributed in different environments, and especially across the globe.You want to be able to manage different WAF appliances without needing to connect to each appliance separately. This means your WAF solution needs to integrate with a Centrallized Management platform, allowing you to build, maintain, and enforce a unified security policy across your entire organization.WAF management
  6. Application Vulnerability PreventionWeb application vulnerabilities are among the most common causes of data breaches. Vulnerabilities—unique to each application—leave companies’ web infrastructures exposed to attacks such as cross-site scripting, SQL injections, cookie poisoning, and others.When defects and vulnerabilities are found in software code, your WAF should rapidly apply fixes (virtual patches) to prevent exploitation by an attacker.This virtual patching requires no immediate changes to the software, and it allows organizations to secure applications immediately—and in some cases, automatically—upon dynamic application testing. Virtual patches are a key component of a strong WAF, often requiring integration with a vulnerability scanner.In addition, your WAF solution should integrate with points such as security information event management systems (SIEM), log retention systems, identity management, incident management, and application scanners to provide layered and automated security. –

What is the purpose of a firewall in application deployment?

A network firewall commonly serves as a primary line of defense against external threats to your organization’s computer systems, networks, and critical information. Firewalls can also be used to partition your organizations internal networks, reducing your risk from insider attacks.

DDOS How A WAF Works

Types of web application firewalls (WAF)

1. Hardware-Based Web Application Firewall

A hardware-based WAF is deployed through a hardware appliance, installed locally within the local area network (LAN) close to the web and application servers. An operating system runs within the appliance, supporting software configurations and updates. 

The greatest advantage of a hardware-based WAF is fast speed and high performance. Due to its physical proximity to the server, it tracks and filters data packets to and from the website with very low latency. The major downside is that owning and maintaining hardware machines is not cheap. From acquisition and installation to storage and maintenance, hardware-based WAFs are associated with higher costs compared to other types of WAFs.

Who is it suitable for? 

A hardware-based WAF is commonly used by large organizations who gain hundreds of thousands of visits on a daily basis. This is because to serve this massive amount of clients efficiently, speed and performance become the highest priority. Besides, most large businesses can easily afford the management and operating costs of running hardware.

Recommended product: WAPPLES

WAPPLES  is a hardware-based WAF that comes with an application delivery controller (load balancer), saving the hassle of purchasing them separately. Unlike most competitors who rely on a signature-based detection system, WAPPLES runs on a patented COCEPTM engine that relies on rule-based detection algorithms. Having a rule-based detection system not only makes it much easier to update, but also maximizes delivery speed and application performance, making it one of the most efficient WAFs in the industry.

2. Software-Based Web Application Firewall

A software-based WAF is installed in a virtual machine (VM) instead of a physical hardware appliance. All the WAF components are essentially the same as a hardware WAF. The only difference is that users would need to have their own hypervisor to run the virtual machine.

A hardware-based WAF is like consuming coffee in a coffee shop, while a software-based WAF is like getting it through a drive-thru, where the customer brings their own place (i.e. the car) for consumption.

The main advantage of a software-based WAF is flexibility. Not only can it be used within an on-premises system, the virtual machine can also be deployed in the cloud, connecting to cloud-based web and application servers. A software WAF is also a cheaper option compared to hardware WAFs. However, the major downside is that since it is run in a virtual machine, a higher latency is experienced during the monitoring and filtering process, making it less speedy than a hardware WAF.

Who is it suitable for?

Clearly, software WAFs are commonly used for organizations with web and application servers based in the cloud, such as data centers and hosting providers. They are also popular among small and medium-sized enterprises who need to protect their web applications at lower costs. 

Recommended Product: WAPPLES SA

WAPPLES SA (software appliance) is a software-based WAF that comes with all the same functionalities and features as WAPPLES. It supports popular hypervisors including KVM, XenServer, and vSphere. It can be optimized for public cloud servers based in AWS, Google Cloud, Microsoft Azure as well as private cloud servers based in VMWare and Citrix.

3. Cloud-Based Web Application Firewall

A cloud-based WAF is a newer generation of WAF that is provided and managed directly by a service provider in the form of SaaS (software-as-a-service). Unlike a software-based WAF, the WAF components are entirely located in the cloud, so that the user does not need to install anything locally or in any virtual machines.

The major advantage is simplicity. The user does not need to install any software physically and only needs to enroll in a subscription plan. The service provider provides all the optimization and updates so that the user is not required to manage the WAF by themselves. On the other hand, the disadvantage is that since the WAF is entirely managed by the service provider, there is not much room for customization.

Who is it suitable for?

Cloud-based WAFs are suitable for most small and medium-sized organizations, since it does not require any physical storage place and manual maintenance, it is great for organizations without many extra resources to manage a WAF.

Recommended Product: Cloudbric

Cloudbric is a SECaaS (security-as-a-service) product that offers web application protection, advanced DDoS protection, and content delivery network (CDN) services in a combined package. Whether the application is hosted locally or in the cloud, Cloudbric provides the easiest protection and maintenance services.


web application firewall (WAF) helps protect a company’s web applications by inspecting and filtering traffic between each web application and the internet. A WAF can help defend web applications from attacks such as cross-site request forgery (CSRF), cross-site-scripting (XSS), file inclusion, and SQL injection.

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