THIS IS A EXPERIMENTAL DETECTION
This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.
The following analytic identifies the usage of Exchange PowerShell modules that were recently used for a proof of concept related to ProxyShell. Currently, there is no active data shared or data we could re-produce relate to this part of the ProxyShell chain of exploits.
Inherently, the usage of the modules is not malicious, but reviewing parallel processes, and user, of the session will assist with determining the intent.
Module - New-MailboxExportRequest will begin the process of exporting contents of a primary mailbox or archive to a .pst file.
Module - New-managementroleassignment can assign a management role to a management role group, management role assignment policy, user, or universal security group (USG).
- Type: TTP
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2022-05-02
- Author: Michael Haag
- ID: 2d10095e-05ae-11ec-8fdf-acde48001122
Kill Chain Phase
1 2 3 4 5 `powershell` EventCode=4104 ScriptBlockText IN ("*New-MailboxExportRequest*", "*New-ManagementRoleAssignment*") | stats count min(_time) as firstTime max(_time) as lastTime by lastTime by Opcode Computer UserID EventCode ScriptBlockText | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `exchange_powershell_module_usage_filter`
The SPL above uses the following Macros:
exchange_powershell_module_usage_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/126.96.36.199/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.
Known False Positives
Administrators or power users may use this PowerShell commandlet for troubleshooting.
Associated Analytic Story
|15.0||30||50||Local user discovery enumeration using PowerShell on $dest$ 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.
source | version: 2