ID | Technique | Tactic |
---|---|---|
T1136.003 | Cloud Account | Persistence |
Detection: Azure AD External Guest User Invited
Description
The following analytic detects the invitation of an external guest user within Azure AD. It leverages Azure AD AuditLogs to identify events where an external user is invited, using fields such as operationName and initiatedBy. Monitoring these invitations is crucial as they can lead to unauthorized access if abused. If confirmed malicious, this activity could allow attackers to gain access to internal resources, potentially leading to data breaches or further exploitation of the environment.
Search
1`azure_monitor_aad` operationName="Invite external user"
2| rename properties.* as *
3| rename initiatedBy.user.userPrincipalName as initiatedBy
4| rename targetResources{}.type as type
5| stats count min(_time) as firstTime max(_time) as lastTime values(user) as user by type, initiatedBy, result, operationName
6| `security_content_ctime(firstTime)`
7| `security_content_ctime(lastTime)`
8| `azure_ad_external_guest_user_invited_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
Azure Active Directory Invite external user | Azure | 'azure:monitor:aad' |
'Azure AD' |
Macros Used
Name | Value |
---|---|
azure_monitor_aad | sourcetype=azure:monitor:aad |
azure_ad_external_guest_user_invited_filter | search * |
azure_ad_external_guest_user_invited_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
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. This analytic was written to be used with the azure:monitor:aad sourcetype leveraging the AuditLogs log category.
Known False Positives
Administrator may legitimately invite external guest users. Filter as needed.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
External Guest User $user$ initiated by $initiatedBy$ | 45 | 50 | 90 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | Azure AD |
azure:monitor:aad |
Integration | ✅ Passing | Dataset | Azure AD |
azure:monitor:aad |
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 4