Exchange PowerShell Snap-Ins Usage — Sigma Rule

Rule metadata and linked tags

Author: FPT.EagleEye, Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: high. Source dates: 2021-03-03 / 2023-03-24.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 569cb7447de1447c2825f97973cf1429086408554f8216c2a14cbde5fb8554df

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Exchange PowerShell Snap-Ins Usage
id: 25676e10-2121-446e-80a4-71ff8506af47
status: test
description: Detects adding and using Exchange PowerShell snap-ins to export mailbox data. As seen used by HAFNIUM and APT27
references:
    - https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/
    - https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
    - https://www.intrinsec.com/apt27-analysis/
author: FPT.EagleEye, Nasreddine Bencherchali (Nextron Systems)
date: 2021-03-03
modified: 2023-03-24
tags:
    - attack.execution
    - attack.t1059.001
    - attack.collection
    - attack.t1114
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_cli:
        CommandLine|contains: 'Add-PSSnapin'
    selection_module:
        CommandLine|contains:
            - 'Microsoft.Exchange.Powershell.Snapin'
            - 'Microsoft.Exchange.Management.PowerShell.SnapIn'
    filter_msiexec:
        # ParentCommandLine: C:\Windows\System32\MsiExec.exe -Embedding C9138ECE2536CB4821EB5F55D300D88E E Global\MSI0000
        ParentImage: 'C:\Windows\System32\msiexec.exe'
        CommandLine|contains: '$exserver=Get-ExchangeServer ([Environment]::MachineName) -ErrorVariable exerr 2> $null'
    condition: all of selection_* and not 1 of filter_*
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/
• https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
• https://www.intrinsec.com/apt27-analysis/