Azure AD Service Principal Authentication

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

The following analytic identifies authentication events of service principals in Azure Active Directory. It leverages the `azure_monitor_aad` data source, specifically targeting "Sign-in activity" within ServicePrincipalSignInLogs. This detection gathers details such as sign-in frequency, timing, source IPs, and accessed resources. Monitoring these events is significant for SOC teams to distinguish between normal application authentication and potential anomalies, which could indicate compromised credentials or malicious activities. If confirmed malicious, attackers could gain unauthorized access to resources, leading to data breaches or further exploitation within the environment.

name: Azure AD Service Principal Authentication
id: 5a2ec401-60bb-474e-b936-1e66e7aa4060
version: 12
creation_date: '2024-02-14'
modification_date: '2026-05-13'
author: Mauricio Velazco, Splunk
status: production
type: TTP
description: The following analytic identifies authentication events of service principals in Azure Active Directory. It leverages the `azure_monitor_aad` data source, specifically targeting "Sign-in activity" within ServicePrincipalSignInLogs. This detection gathers details such as sign-in frequency, timing, source IPs, and accessed resources. Monitoring these events is significant for SOC teams to distinguish between normal application authentication and potential anomalies, which could indicate compromised credentials or malicious activities. If confirmed malicious, attackers could gain unauthorized access to resources, leading to data breaches or further exploitation within the environment.
data_source:
    - Azure Active Directory Sign-in activity
search: |-
    `azure_monitor_aad` operationName="Sign-in activity" category=ServicePrincipalSignInLogs
      | rename properties.* as *
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY dest user src
           vendor_account vendor_product resourceDisplayName
           resourceId signature
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `azure_ad_service_principal_authentication_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: Service Principals will legitimally authenticate remotely to your tenant. Implementing this detection after establishing a baseline enables a more accurate identification of security threats, ensuring proactive and informed responses to safeguard the Azure AD environment. source ips.
references:
    - https://attack.mitre.org/techniques/T1078/004/
    - https://learn.microsoft.com/en-us/entra/identity/monitoring-health/concept-sign-ins#service-principal-sign-ins
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"
finding:
    title: Service Principal $user$ authenticated from $src$
    entity:
        field: user
        type: user
        score: 50
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - Azure Active Directory Account Takeover
    - NOBELIUM Group
asset_type: Azure Active Directory
mitre_attack_id:
    - T1078.004
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/T1078.004/azure_ad_service_principal_authentication/azure_ad_service_principal_authentication.log
          source: Azure AD
          sourcetype: azure:monitor:aad
      test_type: unit

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

35275f91-7597-4e64-be57-58a543af97d1

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