AWS EKS Anonymous Request Authorized by Unusual User Agent

Last updated 2 days ago on 2026-10-21

Created 3 months ago on 2026-08-03

About

This rule detects when an unauthenticated user request is authorized within the cluster via an unusual user agent. Attackers may attempt to use anonymous accounts to gain initial access to the cluster or to avoid attribution of their activities within the cluster. This rule excludes the /healthz, /livez, /version and /.well-known/oauth-authorization-server endpoints which are commonly accessed anonymously.

Tags

Domain: CloudDomain: ContainersPlatform: AWSPlatform: KubernetesData Source: AWSData Source: Amazon Web ServicesData Source: Kubernetes API Server Audit LogsService: AWS EKSUse Case: Threat DetectionTactic: Initial AccessRule Type: New TermsProfile: BetaLanguage: kuery

Severity

medium

Risk Score

MITRE ATT&CK™

Initial Access (TA0001)(external, opens in a new tab or window)

↳ Valid Accounts (T1078)(external, opens in a new tab or window)

False Positive Examples

Anonymous access to the API server is a dangerous setting enabled by default. Common anonymous connections (e.g., health checks) have been excluded from this rule. All other instances of authorized anonymous requests should be investigated.

License

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

Definition

Rule Type: New Terms Rule
Integration Pack: Prebuilt Security Detection Rules
Index Patterns: logs-aws.eks_audit-*
Related Integrations: aws(external, opens in a new tab or window)
Query

✄𐘗text code block:
✄𐘗data_stream.dataset:"aws.eks_audit" and
aws.eks.audit.annotations.authorization_k8s_io/decision:"allow" and
(aws.eks.audit.user.username:("system:anonymous" or "system:unauthenticated") or
aws.eks.audit.impersonatedUser.username:("system:anonymous" or "system:unauthenticated")) and
user_agent.original:(* and not (*kubernetes/$Format)) and
not aws.eks.audit.requestURI:(/healthz* or /livez* or /readyz* or /version)

Install detection rules in Elastic Security

Detect AWS EKS Anonymous Request Authorized by Unusual User Agent 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).