Azure Kubernetes CronJob — Sigma Rule

Rule metadata and linked tags

Author: Austin Songer @austinsonger. Source status: test; severity: medium. Source dates: 2021-11-22 / 2022-12-18.

{
  "product": "azure",
  "service": "activitylogs"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: eb9b3491910e7458dc8eda3286f21289e8f2f6b070c9c075cf1cbe0b8280f1e1

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Azure Kubernetes CronJob
id: 1c71e254-6655-42c1-b2d6-5e4718d7fc0a
status: test
description: |
  Identifies when a Azure Kubernetes CronJob runs in Azure Cloud. Kubernetes Job is a controller that creates one or more pods and ensures that a specified number of them successfully terminate.
  Kubernetes Job can be used to run containers that perform finite tasks for batch jobs. Kubernetes CronJob is used to schedule Jobs.
  An Adversary may use Kubernetes CronJob for scheduling execution of malicious code that would run as a container in the cluster.
references:
    - https://learn.microsoft.com/en-us/azure/role-based-access-control/resource-provider-operations#microsoftkubernetes
    - https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/
    - https://kubernetes.io/docs/concepts/workloads/controllers/job/
    - https://www.microsoft.com/security/blog/2020/04/02/attack-matrix-kubernetes/
author: Austin Songer @austinsonger
date: 2021-11-22
modified: 2022-12-18
tags:
    - attack.persistence
    - attack.t1053.003
    - attack.privilege-escalation
    - attack.execution
logsource:
    product: azure
    service: activitylogs
detection:
    selection:
        operationName|startswith:
            - 'MICROSOFT.KUBERNETES/CONNECTEDCLUSTERS/BATCH'
            - 'MICROSOFT.CONTAINERSERVICE/MANAGEDCLUSTERS/BATCH'
        operationName|endswith:
            - '/CRONJOBS/WRITE'
            - '/JOBS/WRITE'
    condition: selection
falsepositives:
    - Azure Kubernetes CronJob/Job may be done by a system administrator.
    - If known behavior is causing false positives, it can be exempted from the rule.
level: medium

Original YAML and metadata in JSON

False positives

• Azure Kubernetes CronJob/Job may be done by a system administrator.
• If known behavior is causing false positives, it can be exempted from the rule.

Source references

• https://learn.microsoft.com/en-us/azure/role-based-access-control/resource-provider-operations#microsoftkubernetes
• https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/
• https://kubernetes.io/docs/concepts/workloads/controllers/job/
• https://www.microsoft.com/security/blog/2020/04/02/attack-matrix-kubernetes/