Windows whoami.exe Execution With /FO CSV or Output Redirection

Detects whoami.exe runs that request CSV output or indicate output redirection for saved results.

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windows-whoami-exe-execution-with-fo-csv-or-output-redirection-c30fb093

title: Windows whoami.exe Execution With /FO CSV or Output Redirection
id: 6dc0d6ee-3ff0-41f6-b690-9e8fa54d84d6
status: test
description: This rule flags process creation events where whoami.exe is executed with the /FO CSV option to format output as CSV, or where command-line patterns indicate exporting output to a file (including wildcard-style redirection such as whoami*>). Attackers commonly use whoami to enumerate the current user context before further actions, and exporting results can support staging or later collection. The detection relies on Windows process creation telemetry, specifically Image and OriginalFileName fields and CommandLine substring matches for the relevant flags and redirection patterns.
references:
  - https://brica.de/alerts/alert/public/1247926/agent-tesla-keylogger-delivered-inside-a-power-iso-daa-archive/
  - https://app.any.run/tasks/7eaba74e-c1ea-400f-9c17-5e30eee89906/
  - https://www.youtube.com/watch?v=DsJ9ByX84o4&t=6s
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_whoami_output.yml
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2023-02-28
modified: 2023-12-04
tags:
  - attack.discovery
  - attack.t1033
  - car.2016-03-001
logsource:
  category: process_creation
  product: windows
detection:
  selection_main_img:
    - Image|endswith: \whoami.exe
    - OriginalFileName: whoami.exe
  selection_main_cli:
    CommandLine|contains:
      - " /FO CSV"
      - " -FO CSV"
  selection_special:
    CommandLine|contains: whoami*>
  condition: all of selection_main_* or selection_special
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: c30fb093-1109-4dc8-88a8-b30d11c95a5d
    type: derived

What it detects

This rule flags process creation events where whoami.exe is executed with the /FO CSV option to format output as CSV, or where command-line patterns indicate exporting output to a file (including wildcard-style redirection such as whoami*>). Attackers commonly use whoami to enumerate the current user context before further actions, and exporting results can support staging or later collection. The detection relies on Windows process creation telemetry, specifically Image and OriginalFileName fields and CommandLine substring matches for the relevant flags and redirection patterns.

Known false positives

Unknown

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.