O365 Excessive SSO logon errors

SPLUNK detection rule by Rod Soto, Splunk · Apache-2.0

The following analytic detects accounts experiencing a high number of Single Sign-On (SSO) logon errors. It leverages data from the `o365_management_activity` dataset, focusing on failed user login attempts with SSO errors. This activity is significant as it may indicate brute-force attempts or the hijacking/reuse of SSO tokens. If confirmed malicious, attackers could potentially gain unauthorized access to user accounts, leading to data breaches, privilege escalation, or further lateral movement within the organization.

name: O365 Excessive SSO logon errors
id: 8158ccc4-6038-11eb-ae93-0242ac130002
version: 12
creation_date: '2021-01-26'
modification_date: '2026-05-13'
author: Rod Soto, Splunk
status: production
type: Anomaly
description: The following analytic detects accounts experiencing a high number of Single Sign-On (SSO) logon errors. It leverages data from the `o365_management_activity` dataset, focusing on failed user login attempts with SSO errors. This activity is significant as it may indicate brute-force attempts or the hijacking/reuse of SSO tokens. If confirmed malicious, attackers could potentially gain unauthorized access to user accounts, leading to data breaches, privilege escalation, or further lateral movement within the organization.
data_source:
    - O365 UserLoginFailed
search: |-
    `o365_management_activity` Workload=AzureActiveDirectory LogonError=*Sso* Operation=UserLoginFailed
      | stats count min(_time) as firstTime max(_time) as lastTime values(user) as user
        BY src vendor_account vendor_product
           dest signature user_agent
      | where count >= 5
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `o365_excessive_sso_logon_errors_filter`
how_to_implement: You must install splunk Microsoft Office 365 add-on. This search works with o365:management:activity
known_false_positives: Logon errors may not be malicious in nature however it may indicate attempts to reuse a token or password obtained via credential access attack.
references:
    - https://stealthbits.com/blog/bypassing-mfa-with-pass-the-cookie/
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: Excessive number of SSO logon errors from $src$ using UserAgent $user_agent$.
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - Office 365 Account Takeover
    - Cloud Federated Credential Abuse
asset_type: O365 Tenant
mitre_attack_id:
    - T1556
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1556/o365_sso_logon_errors/o365_sso_logon_errors2.json
          sourcetype: o365:management:activity
          source: o365
      test_type: unit

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

91baa970-db2a-46f9-9e69-435eaf9916b9

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