Azure Firewall Rule Collections Modified or Deleted (Activity Logs)

Alerts on Azure Firewall rule collection write or delete operations for Application, NAT, or Network components.

FreeUnreviewedSigmamediumv1

azure-firewall-rule-collections-modified-or-deleted-activity-logs-025c9fe7

title: Azure Firewall Rule Collections Modified or Deleted (Activity Logs)
id: b86b5779-9f96-4c98-8951-a67a27b8e50f
status: test
description: This rule flags Azure Firewall Rule Collection changes where Application, NAT, or Network rule collections are written or deleted. Such activity can indicate an attacker attempting to alter traffic filtering or impair defensive controls by changing firewall behavior. It relies on Azure Activity Log events capturing specific MICROSOFT.NETWORK/AZUREFIREWALLS operation names for WRITE and DELETE actions.
references:
  - https://learn.microsoft.com/en-us/azure/role-based-access-control/resource-provider-operations
  - https://github.com/SigmaHQ/sigma/blob/master/rules/cloud/azure/activity_logs/azure_firewall_rule_collection_modified_or_deleted.yml
author: Austin Songer @austinsonger, Huntrule Team
date: 2021-08-08
modified: 2022-08-23
tags:
  - attack.impact
  - attack.defense-impairment
  - attack.t1686.001
logsource:
  product: azure
  service: activitylogs
detection:
  selection:
    operationName:
      - MICROSOFT.NETWORK/AZUREFIREWALLS/APPLICATIONRULECOLLECTIONS/WRITE
      - MICROSOFT.NETWORK/AZUREFIREWALLS/APPLICATIONRULECOLLECTIONS/DELETE
      - MICROSOFT.NETWORK/AZUREFIREWALLS/NATRULECOLLECTIONS/WRITE
      - MICROSOFT.NETWORK/AZUREFIREWALLS/NATRULECOLLECTIONS/DELETE
      - MICROSOFT.NETWORK/AZUREFIREWALLS/NETWORKRULECOLLECTIONS/WRITE
      - MICROSOFT.NETWORK/AZUREFIREWALLS/NETWORKRULECOLLECTIONS/DELETE
  condition: selection
falsepositives:
  - Rule Collections (Application, NAT, and Network) being modified or deleted may be performed by a system administrator. Verify whether the user identity, user agent, and/or hostname should be making changes in your environment.
  - Rule Collections (Application, NAT, and Network) modified or deleted from unfamiliar users should be investigated. If known behavior is causing false positives, it can be exempted from the rule.
level: medium
license: DRL-1.1
related:
  - id: 025c9fe7-db72-49f9-af0d-31341dd7dd57
    type: derived

What it detects

This rule flags Azure Firewall Rule Collection changes where Application, NAT, or Network rule collections are written or deleted. Such activity can indicate an attacker attempting to alter traffic filtering or impair defensive controls by changing firewall behavior. It relies on Azure Activity Log events capturing specific MICROSOFT.NETWORK/AZUREFIREWALLS operation names for WRITE and DELETE actions.

Known false positives

Rule Collections (Application, NAT, and Network) being modified or deleted may be performed by a system administrator. Verify whether the user identity, user agent, and/or hostname should be making changes in your environment.
Rule Collections (Application, NAT, and Network) modified or deleted from unfamiliar users should be investigated. If known behavior is causing false positives, it can be exempted from the rule.

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