Detection: Azure AD New MFA Method Registered For User

Updated Date: 2024-05-29 ID: 2628b087-4189-403f-9044-87403f777a1b Author: Mauricio Velazco, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the registration of a new Multi-Factor Authentication (MFA) method for an Azure AD account. It leverages Azure AD AuditLogs to identify when a user registers new security information. This activity is significant because adversaries who gain unauthorized access to an account may add their own MFA method to maintain persistence. If confirmed malicious, this could allow attackers to bypass existing security controls, maintain long-term access, and potentially escalate their privileges within the environment.

Search

1 `azure_monitor_aad` category=AuditLogs operationName="User registered security info" properties.operationType=Add 
2| rename properties.* as * 
3| rename targetResources{}.* as * 
4| stats count min(_time) as firstTime max(_time) as lastTime by user, resultDescription, result, src_ip 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `azure_ad_new_mfa_method_registered_for_user_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Azure Active Directory User registered security info	Azure	`'azure:monitor:aad'`	`'Azure AD'`	N/A

Macros Used

Name	Value
azure_monitor_aad	`sourcetype=azure:monitor:aad`
azure_ad_new_mfa_method_registered_for_user_filter	`search *`

azure_ad_new_mfa_method_registered_for_user_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1556	Modify Authentication Process	Credential Access
T1556.006	Multi-Factor Authentication	Defense Evasion

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

FIN13

Scattered Spider

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

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 AuditLogs log category.

Known False Positives

Newly onboarded users who are registering an MFA method for the first time will also trigger this detection.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A new MFA method was registered for user $user$	64	80	80

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`Azure AD`	`azure:monitor:aad`
Integration	✅ Passing	Dataset	`Azure AD`	`azure:monitor:aad`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 3