O365 Mailbox Folder Read Permission Granted
Description
This detection focuses on identifying changes in mailbox folder permissions within an Office 365 environment, specifically pinpointing instances where read permissions are granted. It monitors for two key operations Set-MailboxFolderPermission and Add-MailboxFolderPermission, as logged in the o365_management_activity. These operations are indicative of modifications or additions to the permissions of mailbox folders, potentially altering who can view or interact with the folder contents.
- Type: TTP
-
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2024-03-28
- Author: Mauricio Velazco, Splunk
- ID: cd15c0a8-470e-4b12-9517-046e4927db30
Annotations
ATT&CK
Kill Chain Phase
- Installation
- Exploitation
NIST
- DE.CM
CIS20
- CIS 10
CVE
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`o365_management_activity` Workload=Exchange (Operation="Set-MailboxFolderPermission" OR Operation="Add-MailboxFolderPermission" )
| eval isReadRole=if(match(AccessRights, "^(ReadItems
|Author
|NonEditingAuthor
|Owner
|PublishingAuthor
|Reviewer)$"), "true", "false")
| search isReadRole="true"
| rename UserId as user
| stats count earliest(_time) as firstTime latest(_time) as lastTime by Operation, user, Identity, AccessRights
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `o365_mailbox_folder_read_permission_granted_filter`
Macros
The SPL above uses the following Macros:
o365_mailbox_folder_read_permission_granted_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Required fields
List of fields required to use this analytic.
- _time
- Operation
- AccessRights
- UserId
- Identity
- User
How To Implement
You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
Known False Positives
Mailbox folder permissions may be configured for legitimate purposes, filter as needed.
Associated Analytic Story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
42.0 | 70 | 60 | A folder was granted read permission by $user$ |
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
Reference
- https://attack.mitre.org/techniques/T1098/002/
- https://learn.microsoft.com/en-us/powershell/module/exchange/add-mailboxfolderpermission?view=exchange-ps
- https://learn.microsoft.com/en-us/powershell/module/exchange/set-mailboxfolderpermission?view=exchange-ps
Test Dataset
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 | version: 1