| ID | Technique | Tactic |
|---|---|---|
| T1136.003 | Cloud Account | Persistence |
Detection: O365 SharePoint Allowed Domains Policy Changed
Description
The following analytic identifies when the allowed domain settings for O365 SharePoint have been changed. With Azure AD B2B collaboration, users and administrators can invite external users to collaborate with internal users. External guest account invitations may also need access to OneDrive/SharePoint resources. These changed should be monitored by security teams as they could potentially lead to unauthorized access.
Search
1`o365_management_activity` Workload=SharePoint Operation=SharingPolicyChanged "ModifiedProperties{}.Name"=AllowDomainList
2| eval signature_id = CorrelationId, signature=Operation, src = ClientIP, user = UserId, object_name='ModifiedProperties{}.Name', object_attrs_new = split(replace('ModifiedProperties{}.NewValue',"\.\.\.",""),","), object_attrs_old = split(replace('ModifiedProperties{}.OldValue',"\.\.\.",""),",")
3| stats values(object_attrs_new) as object_attrs_new, values(object_attrs_old) as object_attrs_old, values(src) as src, count, min(_time) as firstTime, max(_time) as lastTime by user,signature,signature_id,object_name
4| eval diff_add=mvmap(object_attrs_new,if(isnull(mvfind(object_attrs_old,object_attrs_new)),object_attrs_new,null))
5| eval diff_remove=mvmap(object_attrs_old,if(isnull(mvfind(object_attrs_new,object_attrs_old)),object_attrs_old,null))
6| eval result = case(isnotnull(diff_add),"Added ".mvjoin(diff_add,","),isnotnull(diff_remove),"Removed ".mvjoin(diff_remove,",")), action = case(isnotnull(diff_add),"created",isnotnull(diff_remove),"deleted")
7| `security_content_ctime(firstTime)`
8| `security_content_ctime(lastTime)`
9| `o365_sharepoint_allowed_domains_policy_changed_filter`
Data Source
| Name | Platform | Sourcetype | Source | Supported App |
|---|---|---|---|---|
| N/A | N/A | N/A | N/A | N/A |
Macros Used
| Name | Value |
|---|---|
| o365_management_activity | sourcetype=o365:management:activity |
| o365_sharepoint_allowed_domains_policy_changed_filter | search * |
o365_sharepoint_allowed_domains_policy_changed_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
MITRE ATT&CK
Kill Chain Phases
NIST
CIS
Threat Actors
KillChainPhase.INSTALLATION
NistCategory.DE_CM
Cis18Value.CIS_10
APT29
LAPSUS$
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 |
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.
Implementation
You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
Known False Positives
Business approved changes by known administrators.
Associated Analytic Story
Risk Based Analytics (RBA)
| Risk Message | Risk Score | Impact | Confidence |
|---|---|---|---|
| The SharePoint Online domain allowlist was changed by $user$, $result$ | 75 | 75 | 100 |
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
References
Detection Testing
| Test Type | Status | Dataset | Source | Sourcetype |
|---|---|---|---|---|
| Validation | ✅ Passing | N/A | N/A | N/A |
| Unit | ✅ Passing | Dataset | o365 |
o365:management:activity |
| Integration | ✅ Passing | Dataset | o365 |
o365:management:activity |
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: 3