PUA - NirCmd Execution

Status: test
Severity: medium
Log source: product windows, category process_creation
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

MITRE ATT&CK coverage

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

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

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

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

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

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

PUA - NirCmd Execution

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_org`

Stage 2: `selection_cmd`

Stage 3: `combo_exec`

Stage 4: `combo_exec_params`

Indicators

Keyboard shortcuts

Search operators

PUA - NirCmd Execution

MITRE ATT&CK coverage

Event coverage

Rule body yaml

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`