Azure AD Multiple AppIDs and UserAgents Authentication Spike

SPLUNK detection rule by Mauricio Velazco, Splunk · Apache-2.0

The following analytic detects unusual authentication activity in Azure AD, specifically when a single user account has over 8 authentication attempts using 3+ unique application IDs and 5+ unique user agents within a short period. It leverages Azure AD audit logs, focusing on authentication events and using statistical thresholds. This behavior is significant as it may indicate an adversary probing for MFA requirements. If confirmed malicious, it suggests a compromised account, potentially leading to further exploitation, lateral movement, and data exfiltration. Early detection is crucial to prevent substantial harm.

name: Azure AD Multiple AppIDs and UserAgents Authentication Spike
id: 5d8bb1f0-f65a-4b4e-af2e-fcdb88276314
version: 14
creation_date: '2023-11-16'
modification_date: '2026-05-13'
author: Mauricio Velazco, Splunk
status: production
type: Anomaly
description: The following analytic detects unusual authentication activity in Azure AD, specifically when a single user account has over 8 authentication attempts using 3+ unique application IDs and 5+ unique user agents within a short period. It leverages Azure AD audit logs, focusing on authentication events and using statistical thresholds. This behavior is significant as it may indicate an adversary probing for MFA requirements. If confirmed malicious, it suggests a compromised account, potentially leading to further exploitation, lateral movement, and data exfiltration. Early detection is crucial to prevent substantial harm.
data_source:
    - Azure Active Directory Sign-in activity
search: |-
    `azure_monitor_aad` category=SignInLogs operationName="Sign-in activity" (properties.authenticationRequirement="multiFactorAuthentication" properties.status.additionalDetails="MFA required in Azure AD") OR (properties.authenticationRequirement=singleFactorAuthentication "properties.authenticationDetails{}.succeeded"=true)
      | bucket span=5m _time
      | rename properties.* as *
      | rename userAgent as user_agent
      | fillnull
      | stats count dc(appId) as unique_app_ids dc(user_agent) as unique_user_agents min(_time) as firstTime max(_time) as lastTime values(dest) as dest values(user_agent) as user_agent
        BY user src vendor_account
           vendor_product signature
      | where count > 5 and unique_app_ids > 2 and unique_user_agents > 5
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `azure_ad_multiple_appids_and_useragents_authentication_spike_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 SignInLogs log category.
known_false_positives: Rapid authentication from the same user using more than 5 different user agents and 3 application IDs is highly unlikely under normal circumstances. However, there are potential scenarios that could lead to false positives.
references:
    - https://attack.mitre.org/techniques/T1078/
    - https://www.blackhillsinfosec.com/exploiting-mfa-inconsistencies-on-microsoft-services/
    - https://github.com/dafthack/MFASweep
    - https://www.youtube.com/watch?v=SK1zgqaAZ2E
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: user
          type: user
          score: 20
          message: $user$ authenticated in a short periof of time with more than 5 different user agents across 3 or more unique application ids.
analytic_story:
    - Azure Active Directory Account Takeover
asset_type: Azure Tenant
mitre_attack_id:
    - T1078
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: identity
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1078/azure_ad_multiple_appids_and_useragents_auth/azure_ad_multiple_appids_and_useragents_auth.log
          source: Azure AD
          sourcetype: azure:monitor:aad
      test_type: unit

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