O365 Mail Permissioned Application Consent Granted by User

Description

The following analytic identifies instances where a user grants consent to an application requesting mail-related permissions within the Office 365 environment. It leverages O365 audit logs, specifically focusing on events related to application permissions and user consent actions. This activity is significant as it can indicate potential security risks, such as data exfiltration or spear phishing, if malicious applications gain access. If confirmed malicious, this could lead to unauthorized data access, email forwarding, or sending malicious emails from the compromised account. Validating the legitimacy of the application and consent context is crucial to prevent data breaches.

Query · spl

`o365_management_activity` Workload=AzureActiveDirectory Operation="Consent to application." ResultStatus=Success | eval admin_consent =mvindex('ModifiedProperties{}.NewValue',0) | search admin_consent=False | eval permissions =mvindex('ModifiedProperties{}.NewValue',4) | rex field=permissions "Scope:(?<Scope>[^,]+)" | makemv delim=" " Scope | search Scope IN ("Mail.Read", "Mail.ReadBasic", "Mail.ReadWrite", "Mail.Read.Shared", "Mail.ReadWrite.Shared", "Mail.Send", "Mail.Send.Shared") | fillnull | stats count min(_time) as firstTime max(_time) as lastTime values(Scope) as Scope by signature dest user src vendor_account vendor_product object ObjectId | `security_content_ctime(lastTime)` | `o365_mail_permissioned_application_consent_granted_by_user_filter`

Implementation guide

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.

Known false positives

  • OAuth applications that require mail permissions may be legitimate, investigate and filter as needed.

Analyst notes

Known false positives: OAuth applications that require mail permissions may be legitimate, investigate and filter as needed.

Raw source O365 Mail Permissioned Application Consent Granted by User · SPL
Esc
Published by splunk/security_content ↗, licensed under Apache 2.0 ↗. Reproduced here unmodified. 
name: O365 Mail Permissioned Application Consent Granted by User
id: fddad083-cdf5-419d-83c6-baa85e329595
version: 9
creation_date: '2023-12-06'
modification_date: '2026-05-13'
author: Mauricio Velazco, Splunk
status: production
type: TTP
description: The following analytic identifies instances where a user grants consent to an application requesting mail-related permissions within the Office 365 environment. It leverages O365 audit logs, specifically focusing on events related to application permissions and user consent actions. This activity is significant as it can indicate potential security risks, such as data exfiltration or spear phishing, if malicious applications gain access. If confirmed malicious, this could lead to unauthorized data access, email forwarding, or sending malicious emails from the compromised account. Validating the legitimacy of the application and consent context is crucial to prevent data breaches.
data_source:
    - O365 Consent to application.
search: "`o365_management_activity` Workload=AzureActiveDirectory Operation=\"Consent to application.\" ResultStatus=Success | eval admin_consent =mvindex('ModifiedProperties{}.NewValue',0) | search admin_consent=False | eval permissions =mvindex('ModifiedProperties{}.NewValue',4) | rex field=permissions \"Scope:(?<Scope>[^,]+)\" | makemv delim=\" \" Scope | search Scope IN (\"Mail.Read\", \"Mail.ReadBasic\", \"Mail.ReadWrite\", \"Mail.Read.Shared\", \"Mail.ReadWrite.Shared\", \"Mail.Send\", \"Mail.Send.Shared\") | fillnull | stats count min(_time) as firstTime max(_time) as lastTime values(Scope) as Scope by signature dest user src vendor_account vendor_product object ObjectId | `security_content_ctime(lastTime)` | `o365_mail_permissioned_application_consent_granted_by_user_filter`"
how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
known_false_positives: OAuth applications that require mail permissions may be legitimate, investigate and filter as needed.
references:
    - https://attack.mitre.org/techniques/T1528/
    - https://www.microsoft.com/en-us/security/blog/2022/09/22/malicious-oauth-applications-used-to-compromise-email-servers-and-spread-spam/
    - https://learn.microsoft.com/en-us/azure/active-directory/manage-apps/protect-against-consent-phishing
    - https://learn.microsoft.com/en-us/defender-cloud-apps/investigate-risky-oauth
    - https://www.alteredsecurity.com/post/introduction-to-365-stealer
    - https://github.com/AlteredSecurity/365-Stealer
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: User $user$ consented an OAuth application that requests mail-related permissions.
    entity:
        field: user
        type: user
        score: 50
analytic_story:
    - Office 365 Account Takeover
asset_type: O365 Tenant
mitre_attack_id:
    - T1528
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/T1528/o365_user_consent_mail_permissions/o365_user_consent_mail_permissions.log
          source: o365
          sourcetype: o365:management:activity
      test_type: unit

Detection rules belong to the projects that publish them and remain under their own licenses. This site indexes and links to them; it claims no rights in them.