What Is Web Application Firewall (WAF)?

What is a Web Application Firewall (WAF)?

A Web Application Firewall (WAF) can be viewed as a protection layer for web applications that inspects traffic in and out to identify suspicious activities.

A WAF can analyze HTTP/HTTPS requests to find the specific patterns that may contain typical attack techniques like SQL injection, XSS, and CSRF.

While the Firewall offers protection at the network layer, WAF is an enhanced security solution applied at the application layer to protect the essential operations of web applications and guard against leaks.

Also Read: What is SSL and CDN? How CDNs Improve SSL / TLS Performance?

WAFs can be implemented as software that runs on traditional servers, specialized hardware devices, or a cloud service, making them useful for various configurations.

It can be set to allow or deny access to specific applications based on their security needs. Another advantage of a WAF is that, unlike simple filters that work based on predefined rules, it constantly examines web traffic, protecting against not only known threats but also newly developed ones.

What’s beneficial for web application owners is that users and other stakeholders are confident that the applications are reliable and available.

How does a web application firewall (WAF) work?

A Web Application Firewall (WAF) is a hardware or software system placed between web applications and the internet, and plays a vital role in defending against various Web Application security threats.

It works because it monitors all HTTP/HTTPS connections in and out, searching for threats in every request-response cycle.

WAF is programmed to detect predefined web attacks and act on them to counter web-based threats such as SQL injection, cross-site scripting (XSS), and cross-site request forgery (CSRF).

This type of filtering mechanism is used based on the rules that ensure the attacker’s traffic does not get into the web application and compromise its data.

Other than static rules, Modern WAFs use behavior-based analysis to capture new threats, which may be new or changing traffic patterns in the traffic.

Since all traffic is filtered and recorded, WAFs offer crucial analytics to administrators in the event of potential security breaches, allowing action to be taken swiftly and efficiently.

This logging capability provides forensic review in the event of a breach. It provides organizations with a mechanism for proving compliance when reviewing activities that occurred on the web.

Why is WAF Security Important?

Protection Against Common Threats

Web Application Firewalls (WAFs) are beneficial as they protect against a broad range of threats common to web applications, including SQL injection, XSS, and CSRF.

WAFs mediate HTTP/HTTPS traffic to stop bad actors from targeting holes in web apps, protect data, and guarantee the soundness of web services.

Compliance with Security Standards

In many industries and regulatory bodies, measures must be implemented to ensure the security of disclosed information.

Organizations are in a position to meet the requirements of compliance standards like PCI-DSS, HIPAA, and GDPR through the implementation of WAFs, which offer the required security measures needed to protect data and privacy.

This compliance helps the organization clear of legal consequences and encourages customers and business partners to trust the organization.

Zero-Day Attack Mitigation

The WAF can help in mitigating zero-day attacks, whereby such vulnerabilities are exploited before any fix is developed.

Due to the possibility of analyzing traffic patterns and employing generally known behavioral heuristics, WAFs can recognize potentially malicious activities that point to a brand-new threat and prevent it; this makes the WAF layer serve as a barrier against newly developed exploits.

Enhanced Visibility and Monitoring

WAFs offer descriptions of web traffic and possible security concerns, allowing administrators to track and investigate malicious operations in a live environment.

This is helpful in the identification of the type and pattern of attacks or the kind of threats that need to be protected, besides facilitating fast containment of the attacks or threats.

The logging and reporting functions of the WAFs help ensure that security monitoring and improvement are done in real time.

Reduced Downtime and Business Continuity

Some of the impacts of cyber attacks on web applications are downtime, interruption of business activities, and losses. WAFs are useful in ensuring that web applications stay operational and are not subject to disruptions through specific attacks.

As the web services remain up and running with WAF’s help, the business continuity and the organization’s reputation are safeguarded.

What are Network-based, Host-based, and Cloud-based WAFs?

Network-based WAFs

Network-based WAFs are usually situated on the network perimeter as a part of the network system. These WAFs sit at the pipeline and observe and scrutinize traffic that is between the internet and protected web applications.

They have less latency and high performance because they are located near the application. Network-based WAFs can process an increased amount of traffic, which makes them appropriate for large businesses. It protects against web-based threats such as SQL injection and cross-site scripting (XSS).

Host-based WAFs

Some WAFs are deployed at the host level, meaning they are implemented within the web server or the application hosting environment.

These WAFs offer precise control over the traffic that passes through them and can be configured according to an application’s requirements.

Traditional network-based WAFs are designed to mediate information exchange on a host’s application level, providing comprehensive information and specific protection.

They are well-suited for organizations where web applications are critical to the business and where organizations have the skills to manage and implement these solutions.

However, they can be very resource-intensive on the server side and may influence the performance of other apps.

Cloud-based WAFs

There are also cloud-based WAFs where the service is delivered via the internet by a third party who hosts the application. These WAFs are, therefore, suitable to provide flexible, scalable, and easy-to-deploy web application protection.

With cloud-based WAFs, the service provider is fully responsible for managing and maintaining it; thus, there is no requirement for human resources with a technical background or extra hardware to support the system.

They can also easily leverage cloud-based intelligence and updates to adapt to any changes in threat environments. These WAFs are ideal for any business venture, especially a small business needing cheap, easy, and simple protection.

Some benefits of cloud-based WAFs include the following: the solutions guard against various forms of attacks, including DDoS and OWASP top 10 vulnerabilities, and the ability to scale to meet requirements in terms of traffic easily.

WAF Security Models

Positive Security Model

The positive security model, or the allowlist-based, also termed the whitelisting model, only allows traffic that is known to be excellent or legitimate in terms of the WAF.

This model entails formulating several rules derived from the proper protocol of HTTP calls that are expected in the web application and that only restrict any other communication.

The primary benefit of this approach is that it is highly useful in eliminating unidentified attacks and new security threats, as only known and approved traffic is admitted.

Compared with other models, this model has a lesser tendency to come up with false positives since it is developed from legitimate traffic patterns.

However, it requires detailed information on legitimate web traffic, and as it is constantly changing because of the dynamic web application, it is potentially more complex to manage.

Negative Security Model

The negative security model, also called the blocklist-based or the signature-based model, stresses protection against known patterns of assaults and malicious actions.

This model has the WAF decide on traffic that needs to be blocked and closed based on specific signatures or patterns or on heuristics.

Establishing instant prevention against various known threats is useful without necessarily considering the application’s legitimate traffic pattern.

However, this type of scanning has limitations; it does not detect new threats and zero-day attacks that do not resemble previous threats.

Besides, it may produce more Synthetic traffic if not fine-tuned, as it operates on the premise of detecting and blocking malicious traffic through patterns.

Hybrid Security Model

The hybrid security model incorporates some positive and negative features to ensure total security.

In this approach, the WAF relies on positive security mode (allowlisting) and negative security mode (blocklisting), with preference being given to the allowlisting mode that identifies and accepts good traffic. In contrast, the blocklisting mode identifies and rejects lousy traffic.

This balanced approach employs the advantages of both models, which provide a proper level of protection against various threats, including exhaustively defined and novel ones.

However, it is very sensitive and needs a lot of tweaking in order to be most effective and disable unwanted false alarms.

Thus, while using both positive and negative models can be challenging compared to a single approach’s slow, steady growth, a hybrid security model gives you the best protection.

Behavioral Security Model

Behavioral security models center around the study of input traffic to recognize peculiarities or these peculiar suspicious activities.

This model entails performing standard profiling of the traffic common in the web application and using behavior analysis techniques to determine the attackers.

The main strength of the behavioral security model is its capability to discover novel threats and attacks that are unknown in the set of traditional signature categories.

It is always active as it is situated to detect new shifting behaviors of the applications that are in use.

However, this approach takes into consideration the learning phase, which is set to provide accurate baselines of normal behavior; therefore, during the learning phase, and especially if the application’s behavior is volatile, it may likely produce false positives or false negatives.

Difference between a WAF, Intrusion Prevention System (IPS), and a Next-Generation Firewall (NGFW)

Aspect	Web Application Firewall (WAF)	Intrusion Prevention System (IPS)	Next-Generation Firewall (NGFW)
Primary Focus	Protects web applications and APIs from specific web-based attacks, such as SQL injection, XSS, and CSRF.	Monitors network traffic for suspicious activities and known attack signatures.	Combines traditional firewall functionalities with advanced features like application awareness and integrated IPS capabilities.
Traffic Inspection	Inspects HTTP/HTTPS traffic specifically, focusing on application-layer threats and vulnerabilities.	Inspects all network traffic (HTTP, FTP, SMTP, etc.) at the network layer to detect and block threats.	Inspects traffic at both the network and application layers, providing granular control over applications and users.
Security Features	Specialized in protecting against web-specific attacks and vulnerabilities present in web applications.	Detects and prevents a wide range of network-based attacks, including malware propagation, port scanning, and brute-force attacks.	Offers a blend of traditional firewall capabilities (like packet filtering and NAT) with advanced security features such as SSL inspection, application control, and intrusion prevention.
Deployment Location	Typically deployed in front of web servers or as part of a web application infrastructure.	Positioned at network choke points (e.g., between internal and external networks) to monitor all traffic.	Positioned at the perimeter of networks or within internal segments to control and secure traffic flows between different network zones.
Granularity of Control	Provides granular control over HTTP/HTTPS traffic, applications, and user access based on specific policies.	Offers detailed control over network protocols, ports, and traffic flows, focusing on network-level attacks and vulnerabilities.	Provides application-aware control over traffic, allowing administrators to define policies based on applications and users, not just IP addresses and ports.
Use Case	Critical for protecting web applications and APIs in data centers or cloud environments against targeted attacks.	Essential for protecting enterprise networks from various cyber threats and ensuring compliance with security policies.	Suitable for organizations needing advanced network security features, application visibility, and control in complex network environments.
Management Complexity	Requires expertise in web application security and specific knowledge of web-based threats and vulnerabilities.	Needs skilled personnel to manage and interpret alerts and logs, with a focus on network security operations.	Demands advanced skills in network security and policy management to leverage application-aware capabilities effectively.
Integration with Other Systems	Often integrated with application delivery controllers (ADCs), SIEM solutions, and threat intelligence platforms.	Can be integrated with SIEMs, endpoint protection systems, and network management tools for centralized security monitoring.	Typically integrates with SIEMs, endpoint security solutions, and cloud-based security platforms for comprehensive threat detection and response.

WAF Features and Capabilities

Web Application Firewalls (WAFs) offer several features and capabilities designed to protect web applications and APIs from a variety of cyber threats.

Here are the key features and capabilities typically found in WAF solutions:

Application-Layer Protection

WAFs specifically target application layer protection or the 7th layer of the OSI model. This includes primary web-based attack vectors such as SQL injection, cross-site scripting (XSS), cross-site request forgery (CSRF), parameter manipulation, and tampering.

Signature-Based Detection

One signature-based detection mechanism that WAFs utilize is pattern and signature recognition. This approach assists in quickly identifying and negating such infamous threats without basing it on behavioral studies alone.

Behavioral Analysis

Leading WAFs incorporate behavioral analysis methods to identify deviations in web traffic. This assists in detecting and preventing zero-day attacks and other forms of threats that the traditional static signature cannot pinpoint.

Protocol Validation

WAFs authenticate incoming requests against the known protocols (HTTP/HTTPS) and other specific protocols to avoid protocol violation incidents, such as HTTP header modifications and other protocol abnormalities.

Data Loss Prevention (DLP)

Some WAFs offer DLP features to block the leakage of specific information via web applications, such as credit card numbers, social security numbers, etc. It is done by content inspection and policy-based control.

Difference between Blocklist and Allowlist WAFs

Aspect	Blocklist WAF	Allowlist WAF
Operation	Blocks traffic based on identified malicious patterns or signatures.	Only allows traffic from sources explicitly listed as safe.
Approach	Reactive approach; blocks known threats or suspicious activities.	Proactive approach; permits only trusted sources or actions.
Focus	Blocks traffic from known malicious entities or identified attack patterns.	Allows traffic only from predefined, trusted sources or actions.
Security	Effective against known threats and commonly identified attack vectors.	Effective against unauthorized access and reduces attack surface.
Flexibility	May require frequent updates to block new threats as they emerge.	Provides strict control over allowed traffic, reducing false positives.
Use Case	Suitable for environments with diverse threat profiles and dynamic attack vectors.	Ideal for applications with stringent security requirements and controlled access.
Configuration	Typically easier to configure initially due to broader filtering criteria.	Requires careful configuration and maintenance to avoid inadvertently blocking legitimate traffic.
Risk Management	Helps mitigate risks associated with broad attack surfaces and diverse threat landscapes.	Reduces exposure to unauthorized access and potential security breaches.

Conclusion

Secure your website and web application now with SiteLock Security, which comes with Web Application Firewall that helps protect web applications by filtering and monitoring HTTP traffic between a web application and the Internet.