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Description

This analytic detects the registration of a new Multi-Factor Authentication (MFA) method associated with a user account within Office 365 by monitoring O365 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.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Authentication
  • Last Updated: 2023-10-20
  • Author: Mauricio Velazco, Splunk
  • ID: 4e12db1f-f7c7-486d-8152-a221cad6ac2b

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1098 Account Manipulation Persistence, Privilege Escalation
T1098.005 Device Registration Persistence, Privilege Escalation
Kill Chain Phase
  • Installation
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`o365_management_activity` Workload=AzureActiveDirectory  Operation="Update user."  
| eval propertyName = mvindex('ModifiedProperties{}.Name', 0) 
| search propertyName = StrongAuthenticationMethod 
| eval oldvalue = mvindex('ModifiedProperties{}.OldValue',0) 
| eval newvalue = mvindex('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) 
|  where count_new_method_type > count_old_method_type 
|  stats earliest(_time) as firstTime latest(_time) as lastTime values(propertyName) by user newvalue oldvalue 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `o365_new_mfa_method_registered_filter`

Macros

The SPL above uses the following Macros:

:information_source: o365_new_mfa_method_registered_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Workload
  • Operation
  • ModifiedProperties{}.Name
  • ModifiedProperties{}.OldValue
  • ModifiedProperties{}.NewValue

How To Implement

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.

Known False Positives

Users may register MFA methods legitimally, investigate and filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
30.0 60 50 A new MFA method was added for $user$

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

Reference

Test Dataset

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 | version: 1