PUA - NirCmd Execution

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the use of NirCmd tool for command execution, which could be the result of legitimate administrative activity

Known false positives

Legitimate use by administrators

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1569.002` System Services: Service Execution

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

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

Stages and Predicates

Stage 0: `condition`

1 of selection_* or all of combo_*

Stage 1: `selection_org`

selection_org:
    - Image|endswith: '\NirCmd.exe'
    - OriginalFileName: 'NirCmd.exe'

Stage 2: `selection_cmd`

selection_cmd:
    CommandLine|contains:
        - ' execmd '
        - '.exe script '
        - '.exe shexec '
        - ' runinteractive '

Stage 3: `combo_exec`

combo_exec:
    CommandLine|contains:
        - ' exec '
        - ' exec2 '

Stage 4: `combo_exec_params`

combo_exec_params:
    CommandLine|contains:
        - ' show '
        - ' hide '

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`exec` corpus 3 (sigma 2, splunk 1) `exec2` `execmd` `hide` `runinteractive` `show` corpus 2 (sigma 1, splunk 1) `.exe script` `.exe shexec`	`field:"CommandLine" kind:match`
`Image`	ends_with	`\NirCmd.exe`	`field:"Image" kind:ends_with value:"\NirCmd.exe"`
`OriginalFileName`	eq	`NirCmd.exe` corpus 2 (sigma 2)	`field:"OriginalFileName" kind:eq value:"NirCmd.exe"`

PUA - NirCmd Execution

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_org

Stage 2: selection_cmd

Stage 3: combo_exec

Stage 4: combo_exec_params

Indicators

Stage 0: `condition`

Stage 1: `selection_org`

Stage 2: `selection_cmd`

Stage 3: `combo_exec`

Stage 4: `combo_exec_params`