Azure Activity Log: Virtual Network Modified or Deleted

Alerts on Azure Activity Log operations that modify (WRITE) or delete (DELETE) Virtual Network resources.

FreeUnreviewedSigmamediumv1

azure-activity-log-virtual-network-modified-or-deleted-bcfcc962

title: "Azure Activity Log: Virtual Network Modified or Deleted"
id: 18f17db3-299f-4d96-9cdb-882bd6c5b06f
status: test
description: This rule flags Azure Activity Log events where a Virtual Network resource is modified or deleted. Attackers may alter or remove network infrastructure to disrupt connectivity or change traffic paths, so these events are important for detecting impact to cloud network configuration. It relies on Activity Log entries with operation names indicating Virtual Networks or Virtual Network Gateways, specifically operations ending in WRITE or DELETE.
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_virtual_network_modified_or_deleted.yml
author: Austin Songer @austinsonger, Huntrule Team
date: 2021-08-08
modified: 2022-08-23
tags:
  - attack.impact
logsource:
  product: azure
  service: activitylogs
detection:
  selection:
    operationName|startswith:
      - MICROSOFT.NETWORK/VIRTUALNETWORKGATEWAYS/
      - MICROSOFT.NETWORK/VIRTUALNETWORKS/
    operationName|endswith:
      - /WRITE
      - /DELETE
  condition: selection
falsepositives:
  - Virtual 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.
  - Virtual 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: bcfcc962-0e4a-4fd9-84bb-a833e672df3f
    type: derived

What it detects

This rule flags Azure Activity Log events where a Virtual Network resource is modified or deleted. Attackers may alter or remove network infrastructure to disrupt connectivity or change traffic paths, so these events are important for detecting impact to cloud network configuration. It relies on Activity Log entries with operation names indicating Virtual Networks or Virtual Network Gateways, specifically operations ending in WRITE or DELETE.

Known false positives

Virtual 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.
Virtual 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.