Securing Kubernetes workloads is more important than ever in today’s fast-changing cloud-native world. Kubernetes pods, the building blocks of modern cloud applications, need extra protection as businesses move faster to the cloud. This blog breaks down the challenges of pod security and explains how KubeArmor helps enforce strong runtime security.

The Kubernetes Security Challenge

The Pod Security Dilemma

At its core, Kubernetes pods present a unique security challenge: all containers within a pod share the same security context. This means binaries across all containers have equal access to volume mount points, service account tokens, and Kubernetes secrets mounted within the pod. While this design enables seamless container communication, it also creates a significant security vulnerability.

Eg. If an attacker successfully exploits a vulnerability in any container within a pod, they gain unrestricted access to all mounted secrets and tokens. This “all-or-nothing” access model makes pods an attractive target for attackers, as evidenced by recent high-profile incidents involving Log4j, Log4Shell, and similar vulnerabilities.

The 3 Pillars of Kubernetes Security

Kubernetes security can be approached through three distinct phases:

1. Static Security: Pre-deployment vulnerability and configuration scanning
2. Admission Control: Policy enforcement during resource creation
3. Runtime Security: Active monitoring and policy enforcement during execution

The Case for Runtime Security

Why Traditional Approaches Fall Short?

Traditional security approaches often focus heavily on static scanning and admission control. However, these methods have limitations:

• Organizations often can’t patch all known vulnerabilities immediately due to operational constraints
• Zero-day vulnerabilities bypass static scanning entirely
• Application updates can invalidate previously established security contexts

Zero Trust Runtime Security

A zero-trust approach to runtime security addresses these limitations by:

• Identifying and enforcing the least permissive security posture
• Continuously monitoring and adapting to application behavior
• Protecting against unknown threats through behavior-based controls

Restricting Pod Behavior

What is an Ideal Runtime Security Engine?

Core Capabilities

It should approach to runtime security through:

1. Process Behavior Control to monitor and restrict process execution
2. File Access Control for governing access to sensitive file systems
3. Network Behavior Management to enforce network policies at runtime
4. LSM Integration necessary to leverage Linux Security Modules for enforcement 

Key Features

• Learning Mode: Observes application behavior to establish baseline policies
• Policy Automation: Automatically generates security policies based on observed behavior
• Multi-Cloud Support: Works across different cloud providers and Linux security modules
• Kubernetes-Native: Deep integration with Kubernetes metadata and resources

Pod Security Context

Implementation Challenges and Solutions

Cross-Platform Compatibility

Different cloud providers support different Linux Security Modules:

• Google Container-Optimized OS → AppArmor
• Amazon Linux 2 → SELinux
• Bottlerocket → SELinux and BPF LSM

AccuKnox, which is built on top of KubeArmor addresses this challenge with a unified policy interface that works across different LSM implementations.

Dynamic Application Updates

Modern applications update frequently, which can invalidate security policies. KubeArmor handles this through:

1. Continuous Learning: Adapting policies based on application changes
2. False Positive Management: Learning from and incorporating feedback
3. Policy Versioning: Maintaining policy history for rollback capability

Pod Security Admission Controller

Security Level	Key Controls	Use Cases	Technical Requirements
Privileged	– No restrictions – Full host access – Capability to modify security contexts	– System containers – Infrastructure pods – Monitoring agents	– No mandatory security context – Allows privileged containers – Full capability set available
Baseline	– Prevents known privilege escalation – Basic pod hardening – Limited host access	– General workloads – Development environments – Internal applications	– Must drop dangerous capabilities – No hostPath volumes – No privileged ports
Restricted	– Enforces pod hardening – Strict security context – Minimal capabilities	– Production workloads – External-facing applications – Multi-tenant environments	– securityContext.runAsNonRoot: true – seccompProfile.type: RuntimeDefault – capabilities.drop: [“ALL”] – allowPrivilegeEscalation: false

Best Practices for Implementation

Threat modeling is essential for securing Kubernetes pods, enabling teams to identify potential threats and implement mitigation strategies. AccuKnox has developed a Kubernetes-native threat modeling template for the Microsoft Threat Modeling Tool (MS-TMT), tailored to K8s entities like pods, namespaces, and clusters. This template helps define trust boundaries specific to Kubernetes environments and generates actionable threat reports for enhancing pod security. Explore the AccuKnox Threat Model and access the K8s-specific template.

1. Start with Observation Mode
   • Deploy KubeArmor in audit mode initially
   • Collect behavioral data without enforcing restrictions
   • Analyze patterns and establish baselines
2. Gradual Policy Enforcement
   • Begin with non-critical workloads
   • Implement policies incrementally
   • Monitor for unintended consequences
3. Regular Policy Review
   • Audit policy effectiveness periodically
   • Update policies based on application changes
   • Monitor for security events and adapt accordingly

AccuKnox builds on KubeArmor to deliver robust runtime security for Kubernetes deployments.

• Offers features like automated policy generation, advanced threat detection, and multi-cluster management.
• Enables zero-trust security for Kubernetes workloads across cloud and on-premises environments.
• Focuses on operational efficiency without impacting application performance or developer workflows.

Static vs Admission vs Runtime Security

Enabling Pod Security Admission (PSA)

To enable Pod Security Admission (PSA), navigate to Inventory → Clusters, select the cluster, and go to View Workloads. Click the cog icon next to the namespace, choose the desired PSA level, and set the mode. For Enforce mode, use Dry Run to preview potential impacts before applying changes. Once reviewed, click Save to apply the PSA.For example, setting PSA to “restricted” prevents privileged Pods from running. If you attempt to deploy a privileged Pod, such as with kubectl run nginx --image=nginx, an error will block the action. This ensures pods adhere to strict security policies, protecting workloads from potential risks.

For the complete step by step tutorial, check out our help documentation.

Kubernetes Pod Security Context: Advanced Security Mechanisms

Kubernetes Pod Security Context represents a sophisticated security configuration mechanism that provides granular control over container runtime environments. At its core, the security context defines comprehensive security parameters that restrict and govern container execution permissions, ensuring minimal attack surface and adherence to principle of least privilege.

The security context encompasses multiple critical security parameters including runAsNonRoot, fsGroup, capabilities, and allowPrivilegeEscalation. These configurations enable administrators to implement precise access controls, preventing potential privilege escalation and unauthorized system interactions. While privileged: true provides complete system access, its usage remains strictly reserved for specialized administrative applications requiring comprehensive system integration.

Namespace-level security policies leverage sophisticated labeling mechanisms to enforce security standards. By implementing pod-security.kubernetes.io labels, administrators can simultaneously enforce baseline policies, generate audit records, and produce user warnings. The nuanced approach allows progressive security implementation without disrupting existing workloads.

The least privilege principle remains paramount in Pod Security Admission configurations. Ideally, organizations should implement the most restrictive security level possible—typically the restricted policy—while maintaining operational flexibility. Admission Controller configurations provide exemption mechanisms for specialized workloads, allowing granular control through username, runtime class, and namespace-based exclusions.

Key security mechanisms include:

• Preventing root-level container execution
• Restricting Linux capabilities
• Defining file system group associations
• Implementing comprehensive audit and warning mechanisms

Pod Security Admission operates exclusively at the pod level, providing a critical layer of runtime security enforcement in Kubernetes environments. By meticulously configuring security contexts, organizations can dramatically reduce potential attack vectors and enhance overall cluster security posture.

Present/Future of Kubernetes Runtime Security

The landscape of Kubernetes security continues to evolve, with several emerging trends:

1. Automated Policy Generation
   • Machine learning-driven policy creation
   • Behavior-based security profiles
   • Continuous policy optimization
2. Enhanced Observability
   • Deep visibility into container behavior
   • Advanced threat detection
   • Real-time security posture assessment
3. Zero Trust Implementation
   • Granular access controls
   • Behavioral baseline enforcement
   • Continuous verification

Conclusion

As Kubernetes deployments become more complex and attacks more sophisticated, runtime security becomes increasingly critical. Tools like KubeArmor, supported by enterprise platforms like AccuKnox, provide the necessary capabilities to implement effective runtime security controls. 

The journey to secure Kubernetes deployments is ongoing, but with the right tools and approaches, organizations can significantly reduce their attack surface while maintaining operational efficiency. Kubernetes is at the core of the cloud native movement.

AccuKnox consults and provides services for Kubernetes pods, clusters, containers to make cloud native deployment safe and resilient against advanced attacks.