O365 Elevated Mailbox Permission Assigned
Description
This detection triggers on the assignment of elevated mailbox permissions within an Office 365 environment, specifically through the Add-MailboxPermission operation, as logged under the Exchange workload in the o365_management_activity. It is meticulously designed to spotlight instances where critical permissions such as FullAccess, ChangePermission, or ChangeOwner are granted, marking significant alterations in mailbox access controls.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Change
- Last Updated: 2024-03-31
- Author: Patrick Bareiss, Mauricio Velazco, Splunk
- ID: 2246c142-a678-45f8-8546-aaed7e0efd30
Annotations
ATT&CK
Kill Chain Phase
- Installation
- Exploitation
NIST
- DE.CM
CIS20
- CIS 10
CVE
Search
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`o365_management_activity` Workload=Exchange Operation=Add-MailboxPermission
| search (AccessRights=FullAccess OR AccessRights=ChangePermission OR AccessRights=ChangeOwner)
| rename Identity AS dest_user
| stats count earliest(_time) as firstTime latest(_time) as lastTime by user dest_user Operation AccessRights
|`security_content_ctime(firstTime)`
|`security_content_ctime(lastTime)`
| `o365_elevated_mailbox_permission_assigned_filter`
Macros
The SPL above uses the following Macros:
o365_elevated_mailbox_permission_assigned_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
- Workload
- Operation
- AccessRights
- user
- src_user
- dest_user
How To Implement
You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
Known False Positives
FullAccess mailbox delegation may be assigned for legitimate purposes, filter as needed.
Associated Analytic Story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
42.0 | 60 | 70 | Elevated mailbox permissions were assigned on $dest_user$ |
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-mailboxpermission
- https://learn.microsoft.com/en-us/exchange/recipients/mailbox-permissions?view=exchserver-2019
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