Web Application Firewall Definition, Working & Role In Security Login

A web application firewall (WAF) defends online applications against application-layer vulnerabilities such as cross-site scripting (XSS), SQL injection, and cookie poisoning. App attacks are the top source of breaches since they provide access to your sensitive data. With the correct web application firewall in place, you can prevent many attacks from exfiltrating that data by compromising your systems.

What Does a Web Application Firewall (WAF) Do?

When a web application firewall is installed in front of a web application, it creates a protective barrier between the web application and the internet, monitoring all communication between the application and the end user (or end users). A WAF protects web apps by filtering, monitoring, and blocking any malicious HTTP/S traffic traveling to the web application and preventing any unauthorized data from leaving the application by adhering to policies that help determine what traffic is malicious and what traffic is safe. In the same way that a proxy server functions as an intermediary to protect a client’s identity, a web application firewall works in the other direction in a typical deployment, functioning as an intermediary to protect the web app server from a potentially dangerous client.

What Is the Role of Web Application Firewall Security?

WAFs are critical for an increasing number of enterprises that provide products or services online, such as mobile app developers, social media providers, and digital banking. A WAF can assist you in protecting sensitive data, such as client details and credit card information, and preventing data leaks.

Most sensitive data is often stored in a backend database accessible via web apps. Mobile applications and IoT devices are rapidly being used by businesses to ease commercial interactions, with many online transactions taking place at the application layer. Attackers frequently target programs to gain access to this data.

Using a web application firewall can assist you in meeting compliance standards such as PCI DSS (the Payment Card Industry Data Security Standard), which applies to any firm that handles cardholder data and necessitates the implementation of a firewall. As a result, a WAF is an integral component of every organization’s security paradigm.

A WAF is necessary, but it is advised to combine it with additional security measures like intrusion detection systems (IDS), intrusion prevention systems (IPS), and traditional firewalls to establish a defense-in-depth security paradigm.

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Web Application Firewalls and Deployment Options

Web Application Firewall

A WAF may be implemented differently, each with its own benefits and drawbacks. WAFs are classified into three types:

In most cases, a network-based WAF is hardware-based. Because it is deployed locally, it reduces latency; nonetheless, it necessitates storing and maintaining physical equipment.

A software-based WAF is controlled by a service provider who provides the WAF as a security service.

Cloud-based WAFs provide an economical and simple-to-implement solution; they often provide a turnkey installation that is as simple as a DNS update to reroute traffic. Cloud-based WAFs also offer a low upfront cost because customers pay for security as a service on a monthly or annual basis. Cloud-based WAFs can also provide a constantly updated solution to guard against the most recent attacks with no additional labor or cost on the user’s part. The disadvantage of using a cloud-based WAF is that customers delegate responsibilities to a third party.

A web application firewall should ideally be able to be implemented in-line, where the solution may act as a “middleman” or as an API-based, out-of-path (OOP) service. An API-based OOP deployment can provide numerous distinct benefits that allow it to be suited for multi-cloud settings. It allows application queries to be routed directly from the client to the application server. Reduced latency, no traffic redirection, greater uptime, and full security across heterogeneous settings are among the benefits.

Web Application Firewall Characteristics and Capabilities

Web application firewalls are commonly equipped with the following characteristics and capabilities:

Databases of attack signatures

Attack signatures are patterns of malicious traffic that include request types, unusual server answers, and known malicious IP addresses. WAFs used to be heavily reliant on attack pattern databases, which were ineffective against new or undiscovered threats.

Traffic pattern analysis enabled by AI

Artificial intelligence systems enable traffic pattern behavioural analysis, employing behavioural baselines for various forms of traffic to discover abnormalities that suggest an attack. This enables you to detect assaults that do not follow well-known harmful patterns.

Profiles of applications

This entails examining the structure of an application, including the common queries, URLs, values, and data types allowed. This enables the WAF to detect and reject potentially malicious requests.


Operators can define the security rules that apply to application traffic. This enables enterprises to tailor WAF behavior to their requirements while avoiding blocking genuine traffic.

Engines for correlating data

Incoming traffic is analyzed and prioritized using known attack signatures, application profiling, AI analysis, and custom rules to decide if it should be stopped.

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Platforms for DDoS protection

A cloud-based platform that guards against distributed denial of service (DDoS) assaults can be integrated. If the WAF detects a DDoS assault, it can route traffic to a DDoS protection platform that can manage a high volume of attacks.

Content distribution networks (CDNs)

Because WAFs are placed at the network edge, a cloud-hosted WAF can provide a CDN to cache the website and reduce load time. The WAF distributes the CDN to numerous global points of presence (PoPs), ensuring that users are served from the nearest PoP.

Models of WAF Security

WAFs can employ either a positive or negative security model or a hybrid of the two:

The positive WAF security concept entails a whitelist that filters traffic based on a list of approved components and actions—anything not on the list is banned. The benefit of this paradigm is that it can detect and prevent new or undiscovered assaults that the developer did not expect.

The negative security concept entails a “blacklist” (or “denylist”) that only prohibits specified items—anything not on the list is permitted. This strategy is simpler to deploy but does not ensure all hazards are addressed. It also necessitates the upkeep of a potentially long list of harmful signatures. The level of security is determined by the number of restrictions imposed.

What Is the Function of a WAF?

Many firms face greater application security concerns due to agile development processes, cloud migration, growing usage of web-based software or SaaS services, and remote workforces. By including a web application firewall, enterprises can respond to assaults on online applications and application programming interfaces (APIs).

While web application firewalls cannot protect enterprises from all digital risks, they address application-level concerns such as the OWASP Top 10 Application Vulnerabilities. These are some examples:

  • Cross-site scripting (XSS): A code injection attack that inserts malicious code into a legitimate website. The code then runs in the user’s web browser as an infected script, allowing the attacker to steal sensitive information or impersonate the user.
  • DDoS Attacks on the Application Layer: A volumetric DoS or DDoS attack directed at the application layer HTTP/S floods, SSL attacks, sluggish and slow attacks, and brute force attacks are common examples.
  • SQL injection: Similar to XSS, SQL injection attacks use a known weakness to insert malicious SQL queries into an application. This enables the hacker to retrieve, modify, or destroy data.
  • Zero-day attacks happen when a hacker takes advantage of an undiscovered security vulnerability or software defect before the program developer releases a fix.
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