Cmd.EXE Missing Space Characters Execution Anomaly

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

Detects Windows command lines that miss a space before or after the /c flag when running a command using the cmd.exe. This could be a sign of obfuscation of a fat finger problem (typo by the developer).

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation
Security-Auditing	Event ID 4688	A new process has been created.

Rule body yaml

title: Cmd.EXE Missing Space Characters Execution Anomaly
id: a16980c2-0c56-4de0-9a79-17971979efdd
status: test
description: |
    Detects Windows command lines that miss a space before or after the /c flag when running a command using the cmd.exe.
    This could be a sign of obfuscation of a fat finger problem (typo by the developer).
references:
    - https://twitter.com/cyb3rops/status/1562072617552678912
    - https://ss64.com/nt/cmd.html
author: Florian Roth (Nextron Systems)
date: 2022-08-23
modified: 2026-05-13
tags:
    - attack.execution
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection1:  # missing space before the /c
        CommandLine|contains:
            - 'cmd.exe/c'
            - '\cmd/c'  # just cmd/c would be prone to false positives
            - '"cmd/c'
            - 'cmd.exe/k'
            - '\cmd/k'  # just cmd/k would be prone to false positives
            - '"cmd/k'
            - 'cmd.exe/r'
            - '\cmd/r'  # just cmd/r would be prone to false positives
            - '"cmd/r'
    selection2: # special cases verified via Virustotal Enterprise search
        CommandLine|contains:
            - '/cwhoami'
            - '/cpowershell'
            - '/cschtasks'
            - '/cbitsadmin'
            - '/ccertutil'
            - '/kwhoami'
            - '/kpowershell'
            - '/kschtasks'
            - '/kbitsadmin'
            - '/kcertutil'
    selection3:  # missing space after the /c
        CommandLine|contains:
            - 'cmd.exe /c'
            - 'cmd /c'
            - 'cmd.exe /k'
            - 'cmd /k'
            - 'cmd.exe /r'
            - 'cmd /r'
    filter_generic:
        CommandLine|contains:
            - 'cmd.exe /c '
            - 'cmd /c '
            - 'cmd.exe /k '
            - 'cmd /k '
            - 'cmd.exe /r '
            - 'cmd /r '
    filter_fp:
        - CommandLine|contains: 'AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules'
        - CommandLine|endswith: 'cmd.exe/c .'
        - CommandLine: 'cmd.exe /c'
        - CommandLine: 'cmd /c'
    condition: 1 of selection* and not 1 of filter_*
falsepositives:
    - Legitimate use of cmd.exe with no arguments e.g. via system("") in C to enable ANSI escape codes
level: high

Stages and Predicates

Stage 0: `condition`

1 of selection* and not 1 of filter_*

Stage 1: `selection1`

selection1:
    CommandLine|contains:
        - 'cmd.exe/c'
        - '\cmd/c'
        - '"cmd/c'
        - 'cmd.exe/k'
        - '\cmd/k'
        - '"cmd/k'
        - 'cmd.exe/r'
        - '\cmd/r'
        - '"cmd/r'

Stage 2: `selection2`

selection2:
    CommandLine|contains:
        - '/cwhoami'
        - '/cpowershell'
        - '/cschtasks'
        - '/cbitsadmin'
        - '/ccertutil'
        - '/kwhoami'
        - '/kpowershell'
        - '/kschtasks'
        - '/kbitsadmin'
        - '/kcertutil'

Stage 3: `selection3`

selection3:
    CommandLine|contains:
        - 'cmd.exe /c'
        - 'cmd /c'
        - 'cmd.exe /k'
        - 'cmd /k'
        - 'cmd.exe /r'
        - 'cmd /r'

Stage 4: `not filter_*`

filter_generic:
    CommandLine|contains:
        - 'cmd.exe /c '
        - 'cmd /c '
        - 'cmd.exe /k '
        - 'cmd /k '
        - 'cmd.exe /r '
        - 'cmd /r '
filter_fp:
    - CommandLine|contains: 'AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules'
    - CommandLine|endswith: 'cmd.exe/c .'
    - CommandLine: 'cmd.exe /c'
    - CommandLine: 'cmd /c'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`CommandLine`	ends_with	`cmd.exe/c .`
`CommandLine`	eq	`cmd /c`
`CommandLine`	eq	`cmd.exe /c`
`CommandLine`	match	`AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules`
`CommandLine`	match	`cmd /c`
`CommandLine`	match	`cmd /k`
`CommandLine`	match	`cmd /r`
`CommandLine`	match	`cmd.exe /c`
`CommandLine`	match	`cmd.exe /k`
`CommandLine`	match	`cmd.exe /r`

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	`"cmd/c` `"cmd/k` `"cmd/r` `/cbitsadmin` `/ccertutil` `/cpowershell` `/cschtasks` `/cwhoami` `/kbitsadmin` `/kcertutil` `/kpowershell` `/kschtasks` `/kwhoami` `\cmd/c` `\cmd/k` `\cmd/r` `cmd /c` corpus 5 (sigma 5) `cmd /k` corpus 4 (sigma 4) `cmd /r` corpus 3 (sigma 3) `cmd.exe /c` corpus 3 (sigma 3) `cmd.exe /k` corpus 3 (sigma 3) `cmd.exe /r` corpus 3 (sigma 3) `cmd.exe/c` `cmd.exe/k` `cmd.exe/r`

`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)

Cmd.EXE Missing Space Characters Execution Anomaly

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection1`

Stage 2: `selection2`

Stage 3: `selection3`

Stage 4: `not filter_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Cmd.EXE Missing Space Characters Execution Anomaly

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection1

Stage 2: selection2

Stage 3: selection3

Stage 4: not filter_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection1`

Stage 2: `selection2`

Stage 3: `selection3`

Stage 4: `not filter_*`