What is a Web Application Firewall?

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What is a Web Application Firewall?

A web application firewall (WAF) is a security solution designed specifically for the protection of web applications from online security threats, malicious agents, and attacks. As reliance upon the digital world grows, so does the security risk, and businesses need to secure their web applications against vulnerabilities that can be exploited for access to sensitive customer and business data. This article will explain how web application firewalls work and what their shortcomings are and will provide a closer look at the different types of WAFs available to businesses.

What is a Web Application Firewall?

There are seven layers in the International Organization for Standardization’s Open Systems Interconnection (OSI) model that enables different types of systems to communicate using standard protocols. Each layer is responsible for a different task and is in communication with the layers above and below it. While the internet does not strictly follow the OSI model, the model is a useful guide for networking.

Web application firewalls primarily operate at the application layer, or top layer, allowing them to oversee and scan data being transmitted rather than being limited to determining threats from the source and destination addresses. This layer is where common internet networking requests are handled, which makes it a common target for certain types of malicious threats.

WAFs examine incoming traffic and run it against a set of predefined rules and known threats to identify and block malicious traffic from reaching the system. These threats can range from SQL injection attacks to cross-site scripting attacks. When the WAF detects one, it can block the traffic stream from proceeding into the application. Meanwhile, it keeps track of the application in its logs for the event analysis.

How do WAFs Work?

There are multiple types of web application firewalls that work differently depending on whether they’re hosted on the application layer or on servers. While they all serve the same purpose, they go about it differently.

Network-based WAFs

A network-based WAF is typically deployed at the edge of the network, usually on dedicated hardware, which allows it to act as a protective barrier between the web application and any incoming unregulated traffic. It works by intercepting incoming traffic and following a set of rules to determine what’s legitimate and what’s harmful.

It works in the same network and environment as the application, ensuring there’s no disconnect between the two, but it’s the most expensive variety of WAF as it requires the maintenance and upkeep of physical servers. Network-based WAFs are best for larger enterprises hosting and running multiple web applications simultaneously.

Host-based WAFs

A host-based WAF is installed directly on the web application’s hosting server. Unlike its network-based counterparts, a host-based firewall works in close proximity to the web application it protects, shielding it from malicious attacks by filtering incoming traffic based on a set of rules pre-defined by the app’s security admin.

It allows for more customization and fine-tuning, making it ideal for applications with specific security requirements, such as finance and healthcare applications that carry extremely sensitive user data. However, host-based WAFs demand a lot of resources to maintain and tend to be complex to set up. They’re less expensive than network-based WAFs but their costs can add up over time.

Cloud-based WAFs

A cloud-based WAF is deployed via a cloud service provider. It can be managed remotely from anywhere, whether the cloud is hosted internally or outsourced, such as in security-as-a-service third-party offerings. It protects against numerous threats and attacks that originate on the web by filtering incoming traffic against a list of known threats and rules, which allows it to determine which traffic is safe.

Unlike network or host-based WAFs, cloud-based WAFs are more affordable as they don’t require on-premises hardware, making them particularly accessible for businesses with limited resources. They’re also highly scalable and great for businesses with highly-fluctuating demand and incoming traffic volume.

Benefits of Using WAFs

Opting to protect your web applications using a WAF comes with numerous advantages, including the following:

Protection Against Common Attacks

WAFs are specifically designed to shield web applications from the most prevalent cyber threats, including cookie poisoning, SQL injection, and cross-site scripting attacks. Thwarting these attacks is critical to maintaining the security and integrity of the web app’s data.

Quick and Easy Deployment

Compared to more comprehensive cybersecurity solutions and firewalls, WAFs are quick and easy to deploy—the most user-friendly solutions can take just a few clicks to set up. This makes them ideal for organizations with limited IT resources or that are in a hurry to deploy a reliable security solution for their web applications.

Customizable Rule Sets

Most WAF vendors and providers include a range of flexibility in their products, allowing custom security rules for blocking specific types of traffic according to the application’s unique requirements and security needs. This ability to customize the level of security ensures that the WAF aligns precisely with an organization’s desired level of protection.

Real-Time Monitoring

By virtue of scanning web application traffic in real time, WAFs can promptly identify potential security incidents to allow immediate response, and keep a detailed log of all events and instances for later analysis. Constant monitoring can also help identify the early signs of an attack through suspicious behavior on the users’ or internal agents’ ends.

Compliance With Industry Standards

Local and federal data laws vary greatly depending on the industry, but having a well-tuned WAF allows businesses to adhere to those regulations and avoid associated fines and penalties. In fact, they play a crucial role in meeting strict compliance regulations, such as the Payment Card Industry Data Security Standard (PCI DSS) or the General Data Protection Regulation (GDPR) for businesses with international and Europe-based clients and users.

WAF Shortcomings

Despite offering a wide range of advantages in terms of protecting web applications, WAFs have some shortcomings and drawbacks. Here are the most important:

False Positives and False Negatives

By relying on scanning incoming traffic against a set of rules and known threats, WAFs can mistakenly flag legitimate traffic as malicious, resulting in a false positive. Alternatively, they may fail at detecting an actual threat, resulting in a false negative, leading to access issues or undetected data breaches.

Complex Configuration

Fine-tuning a WAF to accurately identify threats requires specialized expertise in addition to ongoing updates and maintenance. This can be time-consuming and challenging, particularly for more dynamic and complex web applications.

Performance Impact

Because WAFs need to scan all incoming traffic for malicious activity, they can introduce some latency to the web application, slowing it down and hindering its performance. This effect is exacerbated with larger applications witnessing a large volume of incoming traffic on a regular basis.

Limited Visibility

Because WAFs primarily monitor HTTP and HTTPS traffic, they may be unable to detect attacks coming through other channels as well as more advanced venues of attack, such as zero-day vulnerabilities or distributed attacks like Advanced Persistent Threats (APTs).

Bottom Line: Web Application Firewalls

WAFs have become an indispensable resource for ensuring the security and integrity of online and web applications. Their role in intercepting and preventing potential cyber threats and safeguarding sensitive data is essential not only for regulatory compliance, but also to gain the confidence of customers and business partners alike. Since they work by scanning incoming traffic for signs of malicious intent, they can miss more advanced attacks and cause latency in the application’s performance and response time, but WAFs are an important tool for businesses looking to secure web applications against cyber threats.

Anina Ot
Anina Ot
Anina Ot is a contributor to Enterprise Storage Forum and Datamation. She worked in online tech support before becoming a technology writer, and has authored more than 400 articles about cybersecurity, privacy, cloud computing, data science, and other topics. Anina is a digital nomad currently based in Turkey.

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