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Guides: Kubernetes WAF

Kubernetes WAF: 5 Types of K8s WAFs and How to Choose

What Is Kubernetes WAF?

Kubernetes Web Application Firewall (WAF) is a security measure aimed at safeguarding applications deployed on Kubernetes clusters from a variety of web-related threats and vulnerabilities. It accomplishes this by filtering, monitoring, and blocking harmful HTTP traffic before it reaches the application backend.

A Kubernetes WAF typically incorporates the following:

  • Request inspection: Examines incoming requests for signs of potential attacks, such as SQL injection, cross-site scripting (XSS), or remote file inclusion (RFI).
  • Data validation: Ensures that user input data complies with predefined rules and patterns.
  • Anomaly detection: Recognizes abnormal behavior in web traffic that could signify an attempted attack.
  • Risk scoring: Calculates risk scores based on the probability of an attack succeeding and the magnitude of damage it could cause.

In addition to these primary features, advanced Kubernetes WAF offerings may also include extra capabilities, like API protection, bot management, DDoS mitigation, and integration with other security tools, such as intrusion prevention systems (IPS) or security information and event management (SIEM) platforms.

Editor’s note: Updated to reflect deprecation of NGINX Ingress and the transition to Kubernetes Gateway API.

This is part of a series of articles about Kubernetes security.

In this article:

Why Is WAF Important For Kubernetes Security?

As organizations adopt cloud-native technologies, safeguarding their applications has emerged as a top concern. With the growing adoption of Kubernetes as the preferred container orchestration platform, it is critical to guarantee the protection of your deployments from potential threats.

Tracking current Kubernetes vulnerability and exploit trends helps teams tune WAF rules to the threats their clusters actually face.

Integrating a Web Application Firewall (WAF) in your Kubernetes environment can improve your security posture by:

  • Preventing application layer attacks: A properly configured WAF can prevent unauthorized access to sensitive data by blocking malicious requests and shielding application vulnerabilities, such as SQL injection, cross-site scripting (XSS), and remote file inclusion (RFI).
  • Mitigating DDoS attacks: Distributed Denial-of-Service (DDoS) attacks target web applications by overloading them with massive traffic. Incorporating a WAF in your Kubernetes cluster can help mitigate these attacks before they affect your application servers.
  • Promoting API security: Kubernetes often involves managing APIs, which can be vulnerable to various attacks. A WAF can detect and block these threats, thereby helping to protect your APIs from unauthorized access, data tampering, and other threats.
  • Protecting against malicious bots: Automated bots can conduct credential stuffing, content scraping, and other damaging activities. A WAF can distinguish between human and bot traffic, thereby protecting your applications from bot-induced threats.

Learn more in our detailed Kubernetes firewall guide

5 Types of Kubernetes WAF Tools

1. Kubernetes Gateway API

Gateway API is the Kubernetes project’s new approach to managing traffic, created to address the limitations of the older Ingress model. Ingress controllers translate Ingress rules into proxy configurations and work well for straightforward north-south HTTP/HTTPS routing, SSL termination, and basic load balancing.

As Kubernetes environments grew into larger microservices deployments, Ingress started to show friction. More advanced traffic management patterns (like blue/green or canary rollouts) can become hard to implement cleanly, and heavy use of annotations can reduce portability and make configurations harder to maintain.

Gateway API introduces a more flexible, extensible framework with new resources such as GatewayClass, Gateway, and HTTPRoute. It is protocol-agnostic (supporting HTTP, TCP, gRPC, and more), can cover both north-south and east-west traffic, and includes standardized capabilities in the API specification to reduce “annotation overload” and keep configs cleaner.

2. Standalone WAF Solutions

Standalone WAF solutions are independent tools or services that can be deployed within a Kubernetes environment to provide comprehensive protection for web applications. These WAFs are separate from ingress controllers and can be deployed as sidecar containers alongside application containers or as standalone services within the cluster. Standalone WAF solutions offer greater flexibility in terms of configuration and rule customization, allowing organizations to tailor the WAF to their specific security requirements.

This type of WAF solution may require additional effort to integrate with the existing Kubernetes infrastructure, but it often provides more advanced security features, such as machine learning-based threat detection, bot management, and API security.

3. Cloud-Native WAF Solutions

Cloud-native WAF solutions are offered by cloud providers and are designed specifically for Kubernetes environments. These managed WAF solutions simplify the deployment and management of a WAF in a Kubernetes cluster, often integrating with the cloud provider’s other security offerings for a more comprehensive security solution. Cloud-native WAFs are built to work seamlessly with the cloud provider’s Kubernetes services, ensuring smooth integration and ease of management.

These WAF solutions are designed to be highly scalable, automatically adjusting to the size and needs of your Kubernetes environment. Additionally, they often come with built-in features such as monitoring, logging, and security analytics.

Related content: Read our guide to cloud firewalls

4. Container-Native WAF Solutions

Container-native WAF solutions are designed specifically for containerized environments, providing protection for containerized applications by monitoring and filtering traffic between containers within a Kubernetes cluster. These WAF solutions are built with containerization in mind and offer security features tailored to the unique challenges of containerized environments.

This type of WAF solution focuses on securing communications between containers and services, ensuring that malicious traffic is blocked before it reaches application components. Container-native WAFs may offer additional features such as runtime security, vulnerability scanning, and compliance monitoring.

5. AI and LLM-Aware Kubernetes WAF

AI and large language model (LLM) workloads have changed the role of ingress in Kubernetes. AI inference endpoints are now exposed through REST or gRPC APIs and operate as Tier 1 services. Unlike traditional web apps, each request can trigger expensive GPU-backed computation, which raises both cost and security risks. This makes Layer 7 inspection and WAF-level controls at the cluster edge essential.

AI inference introduces new threat categories that traditional firewalls are not designed to handle. Attackers can exploit cost-based abuse by sending complex prompts that saturate GPUs without causing downtime. Prompt injection attacks target the model’s logic at the application layer, while probing techniques such as model inversion can expose sensitive data. These threats require deep inspection of request payloads before traffic reaches the model.

An AI-aware Kubernetes WAF operates at Layer 7 to inspect and filter traffic before inference begins. It can block abusive or malicious requests, enforce identity-aware access controls, and apply fine-grained rate limits based on request attributes.

How to Choose WAF Solutions for Kubernetes

To choose the most suitable Web Application Firewall (WAF) solution for your Kubernetes cluster, consider various factors that ensure both the security and performance of your applications. Here are some key aspects to keep in mind:

  1. Integration simplicity: Opt for a WAF solution that is easily integrated into your existing Kubernetes infrastructure. It should be compatible with the ingress controllers used in your environment.
  2. Scalability and performance: Seek a WAF that can scale effortlessly alongside your application as it grows, without sacrificing performance. Prefer solutions designed explicitly for containerized environments.
  3. Policies and rule sets: Choose a robust WAF offering adjustable policies and rule sets designed to defend against prevalent web application threats, including SQL injection, cross-site scripting (XSS), and distributed denial-of-service (DDoS) attacks. Prefer solutions that provide pre-configured templates based on industry benchmarks.
  4. Anomaly detection capabilities: For advanced threat protection, real-time monitoring of traffic patterns is necessary to identify anomalies that signal potential attacks. Ensure that your preferred WAF includes machine learning-driven anomaly detection capabilities.
  5. Visibility and reporting: A comprehensive WAF solution should supply in-depth insights into traffic patterns, blocked threats, and security events. This information will empower your security team to assess the efficacy of your WAF implementation and make knowledgeable decisions regarding further enhancements.

Kubernetes WAF with Calico

Calico’s workload-centric WAF enables users to implement policies at the workload level to protect applications from malicious lateral movement within the cluster as well as external communication over the internet. Calico WAF works across any Kubernetes-based platforms, multi-cloud, and hybrid environments, allowing the user to:

  • Monitor application and API traffic within the cluster, leveraging a core ruleset that protects workloads against common OWASP Top 10 threats including SQL injection and cross-site scripting
  • Configure custom rule sets to look for things like unexpected content types that may be indicative of a compromise
  • Use Calico security policies to enforce security controls to block traffic on selected pods on the host

In addition to protecting against application-layer attacks, any blocked HTTP requests are logged and made available in Elasticsearch for review. Calico WAF allows users to trigger alerts based on these logs.

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