Forbidden Request from Unusual User Agent in Kubernetes

Last updated 6 months ago on 2025-07-07

Created 6 months ago on 2025-06-17

About

This rule detects when a forbidden request is made from an unusual user agent in a Kubernetes environment. Adversary tooling may use non-standard or unexpected user agents to interact with the Kubernetes API, which can indicate an attempt to evade detection or blend in with legitimate traffic. In combination with a forbidden request, this behavior can suggest an adversary is attempting to exploit vulnerabilities or misconfigurations in the Kubernetes cluster.

Tags

Data Source: KubernetesTactic: ExecutionLanguage: eql

Severity

medium

Risk Score

MITRE ATT&CK™

Execution (TA0002)(external, opens in a new tab or window)

License

Elastic License v2(external, opens in a new tab or window)

Definition

Rule Type: Event Correlation Rule
Integration Pack: Prebuilt Security Detection Rules
Index Patterns: logs-kubernetes.audit_logs-*
Related Integrations: kubernetes(external, opens in a new tab or window)
Query

✄𐘗text code block:
✄𐘗any where host.os.type == "linux" and event.dataset == "kubernetes.audit_logs" and
kubernetes.audit.stage == "ResponseComplete" and `kubernetes.audit.annotations.authorization_k8s_io/decision` == "forbid" and
not user_agent.original like~ (
  "/", "karpenter", "csi-secrets-store/*", "elastic-agent/*", "agentbeat/*", "insights-operator*", "oc/*", "cloud-defend/*",
  "OpenAPI-Generator/*", "local-storage-operator/*", "falcon-client/*", "nginx-ingress-controller/*", "config-translator/*",
  "kwatch/*", "PrometheusOperator/*", "kube*"
)

Install detection rules in Elastic Security

Detect Forbidden Request from Unusual User Agent in Kubernetes in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).