Suspicious PowerShell Get Current User — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: low. Source dates: 2022-04-04 / not supplied.

{
  "product": "windows",
  "category": "ps_script",
  "definition": "Requirements: Script Block Logging must be enabled"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 1b7cf01d85dd0f2748e17a55f6f28cdc021ff89a778469ff712d6c8d327c1f43

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: Suspicious PowerShell Get Current User
id: 4096a49c-7de4-4da0-a230-c66ccd56ea5a
status: test
description: Detects the use of PowerShell to identify the current logged user.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1033/T1033.md#atomic-test-4---user-discovery-with-env-vars-powershell-script
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1033/T1033.md#atomic-test-5---getcurrent-user-with-powershell-script
author: frack113
date: 2022-04-04
tags:
    - attack.discovery
    - attack.t1033
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains:
            - '[System.Environment]::UserName'
            - '$env:UserName'
            - '[System.Security.Principal.WindowsIdentity]::GetCurrent()'
    condition: selection
falsepositives:
    - Legitimate PowerShell scripts
level: low

Original YAML and metadata in JSON

False positives

• Legitimate PowerShell scripts

Source references

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1033/T1033.md#atomic-test-4---user-discovery-with-env-vars-powershell-script
• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1033/T1033.md#atomic-test-5---getcurrent-user-with-powershell-script