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Description

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
  • Datamodel:
  • Last Updated: 2021-08-27
  • Author: Michael Haag
  • ID: 2d10095e-05ae-11ec-8fdf-acde48001122

ATT&CK

ID Technique Tactic
T1059 Command and Scripting Interpreter Execution
T1059.001 PowerShell Execution
`powershell` EventCode=4104 Message IN ("*New-MailboxExportRequest*", "*New-ManagementRoleAssignment*") 
| stats count min(_time) as firstTime max(_time) as lastTime by Path Message OpCode ComputerName User EventCode
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `exchange_powershell_module_usage_filter`

Associated Analytic Story

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/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Required field

  • _time
  • Path
  • Message
  • OpCode
  • ComputerName
  • User
  • EventCode

Kill Chain Phase

  • Reconnaissance
  • Exploitation

Known False Positives

Administrators or power users may use this PowerShell commandlet for troubleshooting.

RBA

Risk Score Impact Confidence Message
15.0 30 50 Local user discovery enumeration using PowerShell on $dest$ by $user$

Reference

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

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