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.
- Product
- azure
- Service
- activitylogs
- Author
- Austin Songer @austinsonger (SigmaHQ), DRL 1.1
- Published
- 2021-11-25
- Updated
- 2026-07-31
ATT&CK techniques
Initial Access → Cred AccessRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
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
Changelog
v5- v5Candidate ingested via manual entry.2026-07-31
- v4Candidate ingested via manual entry.2026-07-31
- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No 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.
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