Azure Activity Logs: Kubernetes AdmissionRegistration webhook configuration writes

Flags Azure activity log events writing Kubernetes admission webhook configurations (mutating or validating), indicating potential cluster request interception.

FreeReviewedSigma · Medium · v5

Product: azure
Service: activitylogs
Author: Austin Songer @austinsonger (SigmaHQ), DRL 1.1
Published: 2021-11-25
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Initial Access → Cred Access

Recon
Resource Dev
Initial Access
- T1078Valid Accounts
Execution
Persistence
- T1078Valid Accounts
Priv Esc
- T1078Valid Accounts
Defense Evasion
- T1078Valid Accounts
Cred Access
- T1552Unsecured Credentials
- T1552.007Container API
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags write operations to Azure Kubernetes AdmissionRegistration resources, indicating creation or modification of MutatingAdmissionWebhook and ValidatingAdmissionWebhook configuration in connected or managed clusters. Admission webhooks can intercept Kubernetes API requests and potentially alter or validate them, which makes them a persistence and stealth technique if an attacker can deploy malicious webhook behavior. The detection relies on Azure Activity Logs events with operationName patterns for AdmissionRegistration.K8S.IO and webhook configuration writes.

Reporting behind it

Related detections9 linkedT1078 — drag to rearrange

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Suspicious Login Shell Assigned to Service Account games on Linux

Suspicious SSH Daemon Configuration Change Enabling Root Login

Suspicious AWS API Call from TruffleHog Credential Scanner User Agent

Suspicious NTLM Network Logon From Attacker Controlled Workstation Names (via security)

Suspicious dMSA Object Access with Migration AccessMask

Suspicious Access To Kubernetes Service Account Token File

Azure Activity Logs: Kubernetes AdmissionRegistration webhook configuration writes

Pivot detection · T1078 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

azure-activity-logs-kubernetes-admission-webhook-configuration-write-a61a3c56

title: "Azure Activity Logs: Kubernetes AdmissionRegistration webhook configuration writes"
id: f29d530b-5b7e-4599-b7e8-b9577fda1b62
status: test
description: This rule flags write operations to Azure Kubernetes AdmissionRegistration resources, indicating creation or modification of MutatingAdmissionWebhook and ValidatingAdmissionWebhook configuration in connected or managed clusters. Admission webhooks can intercept Kubernetes API requests and potentially alter or validate them, which makes them a persistence and stealth technique if an attacker can deploy malicious webhook behavior. The detection relies on Azure Activity Logs events with operationName patterns for AdmissionRegistration.K8S.IO and webhook configuration writes.
references:
  - https://learn.microsoft.com/en-us/azure/role-based-access-control/resource-provider-operations#microsoftkubernetes
  - https://github.com/SigmaHQ/sigma/blob/master/rules/cloud/azure/activity_logs/azure_kubernetes_admission_controller.yml
author: Austin Songer @austinsonger, Huntrule Team
date: 2021-11-25
modified: 2022-12-18
tags:
  - attack.privilege-escalation
  - attack.initial-access
  - attack.persistence
  - attack.stealth
  - attack.t1078
  - attack.credential-access
  - attack.t1552
  - attack.t1552.007
logsource:
  product: azure
  service: activitylogs
detection:
  selection:
    operationName|startswith:
      - MICROSOFT.KUBERNETES/CONNECTEDCLUSTERS/ADMISSIONREGISTRATION.K8S.IO
      - MICROSOFT.CONTAINERSERVICE/MANAGEDCLUSTERS/ADMISSIONREGISTRATION.K8S.IO
    operationName|endswith:
      - /MUTATINGWEBHOOKCONFIGURATIONS/WRITE
      - /VALIDATINGWEBHOOKCONFIGURATIONS/WRITE
  condition: selection
falsepositives:
  - Azure Kubernetes Admissions Controller may be done by a system administrator.
  - If known behavior is causing false positives, it can be exempted from the rule.
level: medium
license: DRL-1.1
related:
  - id: a61a3c56-4ce2-4351-a079-88ae4cbd2b58
    type: derived

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