O365 Multiple AppIDs and UserAgents Authentication Spike

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

The following analytic identifies unusual authentication activity in an O365 environment, where a single user account experiences more than 8 authentication attempts using 3 or more unique application IDs and over 5 unique user agents within a short timeframe. It leverages O365 audit logs, focusing on authentication events and applying statistical thresholds. This behavior is significant as it may indicate an adversary probing for multi-factor authentication weaknesses. If confirmed malicious, it suggests a compromised account, potentially leading to unauthorized access, privilege escalation, and data exfiltration. Early detection is crucial to prevent further exploitation.

name: O365 Multiple AppIDs and UserAgents Authentication Spike
id: 66adc486-224d-45c1-8e4d-9e7eeaba988f
version: 11
creation_date: '2023-12-06'
modification_date: '2026-05-13'
author: Mauricio Velazco, Splunk
status: production
type: Anomaly
description: The following analytic identifies unusual authentication activity in an O365 environment, where a single user account experiences more than 8 authentication attempts using 3 or more unique application IDs and over 5 unique user agents within a short timeframe. It leverages O365 audit logs, focusing on authentication events and applying statistical thresholds. This behavior is significant as it may indicate an adversary probing for multi-factor authentication weaknesses. If confirmed malicious, it suggests a compromised account, potentially leading to unauthorized access, privilege escalation, and data exfiltration. Early detection is crucial to prevent further exploitation.
data_source:
    - O365 UserLoggedIn
    - O365 UserLoginFailed
search: |-
    `o365_management_activity` Workload=AzureActiveDirectory (Operation=UserLoggedIn OR Operation=UserLoginFailed)
      | bucket span=5m _time
      | stats dc(_raw) as failed_attempts dc(ApplicationId) as unique_app_ids dc(UserAgent) as unique_user_agents values(ApplicationId) values(OS) values(signature) as signature
        BY _time user src
           vendor_account vendor_product dest
      | where failed_attempts > 5 and unique_user_agents > 5 and unique_app_ids > 2
      | `o365_multiple_appids_and_useragents_authentication_spike_filter`
how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
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 period of time with more than 5 different user agents across 3 or more unique application ids.
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - Office 365 Account Takeover
asset_type: O365 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/o365_multiple_appids_and_useragents_auth/o365_multiple_appids_and_useragents_auth.log
          source: o365
          sourcetype: o365:management:activity
      test_type: unit

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ecb491d0-1083-4129-b032-dc890a54e003

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