Kubernetes Anonymous Request Authorized

This rule detects when an unauthenticated user request is authorized within the cluster. 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 and /readyz endpoints which are commonly accessed anonymously.

Rule type: query

Rule indices:

logs-kubernetes.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: None (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://media.defense.gov/2022/Aug/29/2003066362/-1/-1/0/CTR_KUBERNETES_HARDENING_GUIDANCE_1.2_20220829.PDF

Tags:

Data Source: Kubernetes
Tactic: Execution
Tactic: Initial Access
Tactic: Defense Evasion

Version: 6

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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Setup

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The Kubernetes Fleet integration with Audit Logs enabled or similarly structured data is required to be compatible with this rule.

Rule query

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event.dataset:kubernetes.audit_logs
  and kubernetes.audit.annotations.authorization_k8s_io/decision:allow
  and kubernetes.audit.user.username:("system:anonymous" or "system:unauthenticated" or not *)
  and not kubernetes.audit.requestURI:(/healthz* or /livez* or /readyz*)

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Initial Access
- ID: TA0001
- Reference URL: https://attack.mitre.org/tactics/TA0001/
Technique:
- Name: Valid Accounts
- ID: T1078
- Reference URL: https://attack.mitre.org/techniques/T1078/
Sub-technique:
- Name: Default Accounts
- ID: T1078.001
- Reference URL: https://attack.mitre.org/techniques/T1078/001/

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