Kubernetes Runtime Security Tools Compared: Falco, KubeArmor, Sysdig, and Aqua

By Ingrid Svensson | Cloud Architect

The Problem Runtime Security Solves

Scanning container images at build time catches known vulnerabilities before they ship. Network policies restrict lateral movement between pods. But neither of these controls addresses what happens after a container is running: a compromised dependency executes a reverse shell, a misconfigured application writes to /etc/passwd, or a supply chain attack quietly exfiltrates secrets at 2 AM.

Kubernetes runtime security tools close this gap. They observe system calls, file access, process execution, and network activity inside running workloads, then either alert on anomalous behavior or actively block it. For architects running production workloads, the choice of tool determines not just your detection coverage but your blast radius when something goes wrong.

This comparison covers four tools occupying different positions in this space: Falco (open source detection), KubeArmor (open source enforcement), Sysdig Secure (commercial detection platform), and Aqua Security (commercial CNAPP with runtime enforcement). All are actively maintained as of early 2026.

A Critical Architectural Distinction: Detection vs. Enforcement

Before comparing tools, architects need to internalize a fundamental split in this category:

Detection-only tools (Falco, Sysdig Secure) observe behavior and emit alerts. They rely on downstream systems (SIEM, PagerDuty, Slack) to trigger a human or automated response. The workload keeps running during the attack window.

Enforcement tools (KubeArmor, Aqua MicroEnforcer) apply policy inline. They use Linux Security Modules (LSMs) such as AppArmor or SELinux, combined with eBPF hooks, to block forbidden system calls before they complete. Response is sub-millisecond, but policy misconfiguration can break production workloads.

Most mature environments end up with both: an enforcement layer for high-confidence denylists and a detection layer for behavioral anomalies. Understanding this before you evaluate tools saves weeks of re-architecture later.

Falco: The CNCF Standard for Runtime Detection

Falco is the de facto open source standard for Kubernetes runtime threat detection. Originally created by Sysdig, it was donated to the Cloud Native Computing Foundation (CNCF) and graduated to CNCF Graduated status in 2024, joining projects like Kubernetes and Prometheus at the highest maturity tier. The current release as of late 2025 is v0.42.0.

How Falco Works

Falco intercepts Linux system calls using either a kernel module or an eBPF probe. The eBPF driver is now the recommended approach: it does not require kernel source headers and is safer to operate in shared-kernel environments. Captured events are matched against a rule set written in a YAML-based DSL, and matches produce structured output forwarded via Falcosidekick to over 50 output targets.

Sample Falco Rule

- rule: Shell Spawned in Container
  desc: A shell binary was executed inside a container
  condition: >
    container and
    proc.name in (shell_binaries) and
    spawned_process and
    not proc.pname in (known_shell_spawn_parents)
  output: >
    Shell spawned (user=%user.name container=%container.name
    image=%container.image.repository cmd=%proc.cmdline)
  priority: WARNING
  tags: [container, shell, mitre_execution]

Installing Falco via Helm

helm repo add falcosecurity https://falcosecurity.github.io/charts
helm repo update
helm install falco falcosecurity/falco \
  --namespace falco \
  --create-namespace \
  --set driver.kind=ebpf \
  --set falcosidekick.enabled=true \
  --set falcosidekick.webui.enabled=true

Strengths

• Zero licensing cost; CNCF-governed so no single vendor controls the roadmap
• Large default ruleset covering MITRE ATT&CK techniques for containers
• Falcosidekick routes alerts to Slack, Elasticsearch, PagerDuty, and dozens more with a single config
• Wide ecosystem integrations: Helm, Operator, cloud provider marketplaces

Limitations

• Detection only; Falco cannot block a syscall mid-flight
• Custom rule authorship requires understanding of the Falco condition DSL and kernel event fields
• High-cardinality environments (thousands of pods) require careful tuning to avoid alert fatigue

Best For

Teams that want open source runtime visibility without vendor lock-in, or organizations using Falco as the detection backbone underneath a commercial SIEM.

KubeArmor: eBPF-Native Enforcement

KubeArmor is an open source runtime security engine that combines eBPF with Linux Security Modules to enforce policy at the kernel level. Where Falco watches and alerts, KubeArmor watches and blocks. It supports AppArmor, SELinux, and BPF-LSM as enforcement backends, selecting the appropriate one based on the host kernel.

The project’s v0.11+ releases added ARMv9 compatibility, extending runtime enforcement to edge and IoT workloads running on newer ARM processors. AccuKnox provides a commercial management plane for KubeArmor in enterprise environments.

How KubeArmor Works

KubeArmor applies KubeArmorPolicy custom resources that define allowed and blocked operations per workload. Policies target pods by label selectors and can restrict process execution paths, file system access, and network behavior independently.

Sample KubeArmor Policy

apiVersion: security.kubearmor.com/v1
kind: KubeArmorPolicy
metadata:
  name: block-shell-in-payment-service
  namespace: production
spec:
  selector:
    matchLabels:
      app: payment-service
  process:
    matchPaths:
    - path: /bin/bash
    - path: /bin/sh
    - path: /usr/bin/python3
  action: Block
  file:
    matchDirectories:
    - dir: /etc/
      recursive: true
      readOnly: true

Installing KubeArmor via Helm

helm repo add kubearmor https://kubearmor.github.io/charts
helm repo update
helm install kubearmor kubearmor/kubearmor \
  --namespace kubearmor \
  --create-namespace

Strengths

• Inline blocking with sub-millisecond policy enforcement
• Policy-as-code approach integrates naturally with GitOps workflows
• Dual detection and enforcement modes; can run in audit mode first to validate policy before enabling Block
• CNCF project with active maintainership and broad kernel support (4.14+)

Limitations

• Writing accurate enforcement policies requires detailed understanding of each workload’s expected process tree and file access patterns
• Policy misconfiguration can break application functionality; audit-first discipline is essential
• Fewer out-of-the-box alerting integrations than Falco; purpose-built for enforcement

Best For

Teams that need enforcement rather than detection, particularly in regulated environments where “alert and respond” is not fast enough to satisfy compliance requirements.

Sysdig Secure: Commercial Runtime Detection at Scale

Sysdig Secure is the commercial platform Sysdig built around the Falco detection engine. It extends open source Falco with managed threat intelligence, drift detection, compliance reporting, forensics, and a hosted management console. Organizations already running open source Falco often graduate to Sysdig Secure when they need managed rules, cross-cluster correlation, or compliance audit trails.

Key Differentiators Over Open Source Falco

Falco Feeds: Sysdig’s threat research team maintains a continuously updated managed ruleset delivered via the falcoctl CLI. Teams adopt new detection rules without writing or maintaining YAML themselves.

Drift Detection: Sysdig Secure detects executables added to a running container that were not present in the original image, a reliable signal for many attack chains.

Cloud Activity Integration: Beyond syscalls, Sysdig Secure correlates Kubernetes runtime events with AWS CloudTrail, GCP Audit Logs, and Okta events in a unified timeline.

Compliance Reporting: Pre-built reports for SOC 2, PCI-DSS, CIS Kubernetes Benchmark, and NIST SP 800-190 reduce audit preparation time.

Pricing

Sysdig Secure uses per-host pricing. Published data from procurement platforms indicates typical annual contracts ranging from around $7,000 (small deployments) to well over $1 million for large enterprises, with median deals around $138,000 per year. Sysdig does not publish a standard rate card; pricing is negotiated per engagement.

Limitations

• Detection-only at the core (inherits Falco’s architecture); enforcement requires pairing with a policy enforcement tool
• Cost scales with host count, making it expensive for large node pools
• SaaS dependency for the management plane; not suitable for air-gapped environments without the on-premises deployment option

Best For

Mid-size to large enterprises that want managed Falco rules, cross-cluster visibility, and compliance reporting without the operational overhead of self-hosting the detection stack.

Aqua Security: Full CNAPP with Runtime Enforcement

Aqua Security operates as a Cloud Native Application Protection Platform (CNAPP), covering the full lifecycle from image scanning and software supply chain security through to runtime enforcement and cloud posture management. The runtime enforcement component deploys lightweight MicroEnforcer agents into pods and enforces policy using a combination of eBPF hooks and Open Policy Agent (OPA).

Key Runtime Security Features

Kubernetes Assurance Policies: OPA-based policies written in Rego expressions govern what can deploy. Aqua blocks non-compliant workloads from scheduling, not just alerting after the fact.

Drift Prevention: Any process or binary not present in the original image is blocked from executing at runtime, regardless of how it arrived.

CIS Benchmark Scanning: Aqua integrates kube-bench (its own open source project) to run automated CIS Kubernetes Benchmark checks daily, producing pass/fail reports against over 100 individual controls.

Supply Chain to Runtime Correlation: Because Aqua covers both the build pipeline and runtime, it can correlate a runtime anomaly back to its source image layer and the CI job that built it.

Pricing

Aqua Security is enterprise-priced. On the Google Cloud Marketplace, Aqua Container Security is listed at $0.05 to $0.33 per node per hour depending on node size, which translates to roughly $438 to $2,891 per node per year. Enterprise licensing for large deployments typically starts around $50,000 annually; direct contracts are negotiated.

Limitations

• Highest total cost of the tools in this comparison; primarily suitable for organizations with existing security budget
• Deployment complexity: the full CNAPP involves multiple components (scanner, enforcer, console, gateway)
• OPA/Rego policy authorship requires dedicated security engineering time

Best For

Enterprises that need a single platform covering image scanning, runtime enforcement, cloud posture management, and compliance, particularly in regulated industries such as financial services, healthcare, or government.

Comparison Table

Decision Framework: Which Tool for Which Context

Startups and Small Teams

Start with Falco deployed via Helm with Falcosidekick routing alerts to Slack. The default ruleset covers the most common attack patterns with zero licensing cost. Add KubeArmor if you have specific workloads with well-understood process profiles that you want to harden proactively (payment services, credential stores). This combination gives you detection and enforcement without any licensing spend.

Platform Teams Running Multi-Tenant Clusters

The detection-versus-enforcement question becomes more pressing at scale. KubeArmor’s label-selector policies map cleanly to Kubernetes namespaces and workloads, making it the better enforcement choice in multi-tenant environments where each tenant’s allowed process set differs. Pair it with Falco for behavioral detection of anomalies that do not fit a simple denylist pattern.

Enterprises with Compliance Requirements (SOC 2, PCI-DSS, HIPAA)

Sysdig Secure reduces audit prep time through pre-built compliance reports and managed rule feeds. Its ability to correlate Kubernetes runtime events with cloud control plane activity (CloudTrail, GCP Audit Logs) is valuable for incident response timelines that auditors require. For organizations that also need supply chain security and posture management in a single pane of glass, Aqua Security’s CNAPP model eliminates the integration work of assembling those capabilities separately.

Cilium-Native Environments

If your cluster already runs Cilium for networking, Tetragon (the Cilium project’s runtime security component) is the natural complement. It shares the Cilium eBPF data plane, reducing agent overhead, and supports real-time syscall blocking through the same BPF-LSM mechanisms as KubeArmor.

Air-Gapped or High-Security Environments

Both Falco and KubeArmor run fully on-premises with no SaaS dependency. Aqua Security offers an on-premises deployment option. Sysdig Secure’s on-premises option exists but adds deployment complexity. For teams where outbound connectivity to vendor SaaS is not permitted, the open source tools are the cleaner path.

Implementation Sequence

Regardless of which tool you choose, the deployment order that causes the least production disruption follows a consistent pattern:

1. Deploy in audit/detection-only mode first; observe what would have fired for at least two weeks
2. Tune rules or policies to eliminate false positives before enabling any blocking behavior
3. Enable enforcement for stateless, well-understood workloads first (API gateways, proxies)
4. Extend enforcement progressively to stateful workloads with longer validation cycles
5. Integrate alert routing before declaring production-ready; an unrouted alert is no alert at all

Runtime security tools that are not tuned become noise generators. The architecture decision and the operational discipline to tune it are equally important.

🔍 Free tool: K8s YAML Security Linter — paste any Kubernetes manifest and instantly catch security misconfigurations: missing resource limits, privileged containers, host network access, and more.