azure_ad_new_mfa_method_registered.yml

name: Azure AD New MFA Method Registered
id: 0488e814-eb81-42c3-9f1f-b2244973e3a3
version: 2
date: '2023-12-20'
author: Mauricio Velazco, Splunk
status: production
type: TTP
data_source: 
- Azure Active Directory Update user
description: This analytic detects the registration of a new Multi-Factor Authentication (MFA) method associated with a user account within Azure Active Directory by monitoring Azure AD audit logs and configurations. While adding a new MFA method can be a routine and legitimate action, it can also be indicative of an attacker's attempt to maintain persistence on a compromised account. By registering a new MFA method, attackers can potentially bypass existing security measures, allowing them to authenticate using stolen credentials without raising alarms. Monitoring for such changes is crucial, especially if the addition is not preceded by a user request or if it deviates from typical user behavior. If an attacker successfully registers a new MFA method on a compromised account, they can solidify their access, making it harder for legitimate users to regain control. The attacker can then operate with the privileges of the compromised account, potentially accessing sensitive data, making unauthorized changes, or even escalating their privileges further. Immediate action would be required to verify the legitimacy of the MFA change and, if malicious, to remediate and secure the affected account.
search: >-
 `azure_monitor_aad`  operationName="Update user"
 | rename properties.* as * 
 | eval propertyName = mvindex('targetResources{}.modifiedProperties{}.displayName', 0)
 | search propertyName = StrongAuthenticationMethod
 | eval oldvalue = mvindex('targetResources{}.modifiedProperties{}.oldValue',0)
 | eval newvalue = mvindex('targetResources{}.modifiedProperties{}.newValue',0)
 | rex field=newvalue max_match=0 "(?i)(?<new_method_type>\"MethodType\")"
 | rex field=oldvalue max_match=0 "(?i)(?<old_method_type>\"MethodType\")"
 | eval count_new_method_type = coalesce(mvcount(new_method_type), 0)
 | eval count_old_method_type = coalesce(mvcount(old_method_type), 0)
 | stats earliest(_time) as firstTime latest(_time) as lastTime values(propertyName) by user newvalue oldvalue
 | `security_content_ctime(firstTime)`
 | `security_content_ctime(lastTime)`
 | `azure_ad_new_mfa_method_registered_filter`
how_to_implement: You must install the latest version of Splunk Add-on for Microsoft
  Cloud Services from Splunkbase (https://splunkbase.splunk.com/app/3110/#/details). You must be ingesting Azure Active Directory events into your Splunk environment through an EventHub.
  This analytic was written to be used with the azure:monitor:aad sourcetype leveraging the AuditLog log category.
known_false_positives: Users may register MFA methods legitimally, investigate and filter as needed.
references:
- https://attack.mitre.org/techniques/T1098/005/
- https://www.microsoft.com/en-us/security/blog/2023/06/08/detecting-and-mitigating-a-multi-stage-aitm-phishing-and-bec-campaign/
- https://www.csoonline.com/article/573451/sophisticated-bec-scammers-bypass-microsoft-365-multi-factor-authentication.html
tags:
  analytic_story:
  - Azure Active Directory Persistence
  asset_type: Azure Tenant
  confidence: 50
  impact: 60
  message: A new MFA method was registered for user $user$
  mitre_attack_id:
  - T1098
  - T1098.005
  observable:
  - name: user
    type: User
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  risk_score: 30
  required_fields:
  - _time
  - operationName
  - properties.targetResources{}.modifiedProperties{}.displayName
  - properties.targetResources{}.modifiedProperties{}.oldValue
  - properties.targetResources{}.modifiedProperties{}.newValue
  - user
  security_domain: identity
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1098.005/azure_ad_register_new_mfa_method/azure_ad_register_new_mfa_method.log
    source: Azure AD
    sourcetype: azure:monitor:aad