Azure AD Multiple Users Failing To Authenticate From Ip

name: Azure AD Multiple Users Failing To Authenticate From Ip
id: 94481a6a-8f59-4c86-957f-55a71e3612a6
version: 11
date: '2026-03-10'
author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk
status: production
type: Anomaly
description: The following analytic detects a single source IP failing to authenticate with 30 unique valid users within 5 minutes in Azure Active Directory. It leverages Azure AD SignInLogs with error code 50126, indicating invalid passwords. This behavior is significant as it may indicate a Password Spraying attack, where an adversary attempts to gain initial access or elevate privileges by trying common passwords across many accounts. If confirmed malicious, this activity could lead to unauthorized access, data breaches, or privilege escalation within the Azure AD environment.
data_source:
    - Azure Active Directory
search: |-
    `azure_monitor_aad` category=SignInLogs properties.status.errorCode=50126 properties.authenticationDetails{}.succeeded=false
      | rename properties.* as *
      | bucket span=5m _time
      | rename userAgent as user_agent
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime dc(user) as unique_user values(dest) as dest values(user) as user values(user_agent) as user_agent values(vendor_account) as vendor_account values(vendor_product) as vendor_product
        BY src signature
      | where unique_user > 30
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `azure_ad_multiple_users_failing_to_authenticate_from_ip_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 Signin log category.
known_false_positives: A source Ip failing to authenticate with multiple users is not a common for legitimate behavior.
references:
    - https://attack.mitre.org/techniques/T1110/003/
    - https://docs.microsoft.com/en-us/security/compass/incident-response-playbook-password-spray
    - https://www.cisa.gov/uscert/ncas/alerts/aa21-008a
    - https://docs.microsoft.com/azure/active-directory/reports-monitoring/reference-sign-ins-error-codes
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 ("$user$") starthoursago=168  | 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: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: Source Ip $src$ failed to authenticate with 30 users within 5 minutes.
    risk_objects:
        - field: user
          type: user
          score: 20
    threat_objects:
        - field: src
          type: ip_address
tags:
    analytic_story:
        - Azure Active Directory Account Takeover
    asset_type: Azure Active Directory
    mitre_attack_id:
        - T1110.003
        - T1110.004
        - T1586.003
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: identity
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1110.003/password_spraying_azuread/azuread_signin.log
          source: Azure AD
          sourcetype: azure:monitor:aad