PUA - NirCmd Execution — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-01-24 / 2023-02-13.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: aadb9a08f00cd985332bfe2a7f03f4b2a75db79a2e62737d0432ace839de6ea1

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: PUA - NirCmd Execution
id: 4e2ed651-1906-4a59-a78a-18220fca1b22
status: test
description: Detects the use of NirCmd tool for command execution, which could be the result of legitimate administrative activity
references:
    - https://www.nirsoft.net/utils/nircmd.html
    - https://www.winhelponline.com/blog/run-program-as-system-localsystem-account-windows/
    - https://www.nirsoft.net/utils/nircmd2.html#using
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2022-01-24
modified: 2023-02-13
tags:
    - attack.execution
    - attack.t1569.002
    - attack.s0029
logsource:
    category: process_creation
    product: windows
detection:
    selection_org:
        - Image|endswith: '\NirCmd.exe'
        - OriginalFileName: 'NirCmd.exe'
    selection_cmd:
        CommandLine|contains:
            - ' execmd '
            - '.exe script '
            - '.exe shexec '
            - ' runinteractive '
    combo_exec:
        CommandLine|contains:
            - ' exec '
            - ' exec2 '
    combo_exec_params:
        CommandLine|contains:
            - ' show '
            - ' hide '
    condition: 1 of selection_* or all of combo_*
falsepositives:
    - Legitimate use by administrators
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate use by administrators

Source references

• https://www.nirsoft.net/utils/nircmd.html
• https://www.winhelponline.com/blog/run-program-as-system-localsystem-account-windows/
• https://www.nirsoft.net/utils/nircmd2.html#using