Potential CommandLine Obfuscation Using Unicode Characters From Suspicious Image

Status: test
Severity: high
Author: frack113, Florian Roth (Nextron Systems), Josh Nickels
Source: github.com/SigmaHQ/sigma

Detects potential commandline obfuscation using unicode characters. Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1027` Obfuscated Files or Information

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Potential CommandLine Obfuscation Using Unicode Characters From Suspicious Image
id: 584bca0f-3608-4402-80fd-4075ff6072e3
related:
    - id: e0552b19-5a83-4222-b141-b36184bb8d79
      type: similar
    - id: ad691d92-15f2-4181-9aa4-723c74f9ddc3 # RTLO
      type: similar
    - id: 2c0d2d7b-30d6-4d14-9751-7b9113042ab9
      type: obsolete
status: test
description: |
    Detects potential commandline obfuscation using unicode characters.
    Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit.
references:
    - https://www.wietzebeukema.nl/blog/windows-command-line-obfuscation
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1027/T1027.md#atomic-test-6---dlp-evasion-via-sensitive-data-in-vba-macro-over-http
author: frack113, Florian Roth (Nextron Systems), Josh Nickels
date: 2024-09-02
modified: 2025-05-30
tags:
    - attack.stealth
    - attack.t1027
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        Image|endswith:
            - '\cmd.exe'
            - '\cscript.exe'
            - '\powershell.exe'
            - '\powershell_ise.exe'
            - '\pwsh.exe'
            - '\wscript.exe'
        OriginalFileName:
            - 'Cmd.EXE'
            - 'cscript.exe'
            - 'PowerShell.EXE'
            - 'PowerShell_ISE.EXE'
            - 'pwsh.dll'
            - 'wscript.exe'
    selection_special_chars:
        CommandLine|contains:
            # spacing modifier letters that get auto-replaced
            - 'ˣ' # 0x02E3
            - '˪' # 0x02EA
            - 'ˢ' # 0x02E2
            # Forward slash alternatives
            - '∕' # 0x22FF
            - '⁄' # 0x206F
            # Hyphen alternatives
            - '―' # 0x2015
            - '—' # 0x2014
            # Whitespace that don't work as path separator
            - ' ' # 0x00A0
            # Other
            - '¯'
            - '®'
            - '¶'
            # Unicode whitespace characters
            - '⠀' # Braille Pattern Blank (Unicode: U+2800)
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    Image|endswith:
        - '\cmd.exe'
        - '\cscript.exe'
        - '\powershell.exe'
        - '\powershell_ise.exe'
        - '\pwsh.exe'
        - '\wscript.exe'
    OriginalFileName:
        - 'Cmd.EXE'
        - 'cscript.exe'
        - 'PowerShell.EXE'
        - 'PowerShell_ISE.EXE'
        - 'pwsh.dll'
        - 'wscript.exe'

Stage 2: `selection_special_chars`

selection_special_chars:
    CommandLine|contains:
        # spacing modifier letters that get auto-replaced
        - 'ˣ' # 0x02E3
        - '˪' # 0x02EA
        - 'ˢ' # 0x02E2
        # Forward slash alternatives
        - '∕' # 0x22FF
        - '⁄' # 0x206F
        # Hyphen alternatives
        - '―' # 0x2015
        - '—' # 0x2014
        # Whitespace that don't work as path separator
        - ' ' # 0x00A0
        # Other
        - '¯'
        - '®'
        - '¶'
        # Unicode whitespace characters
        - '⠀' # Braille Pattern Blank (Unicode: U+2800)

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	corpus 2 (sigma 2) `®` corpus 2 (sigma 2) `¯` corpus 2 (sigma 2) `¶` corpus 2 (sigma 2) `ˢ` corpus 2 (sigma 2) `ˣ` corpus 2 (sigma 2) `˪` corpus 2 (sigma 2) `—` corpus 2 (sigma 2) `―` corpus 2 (sigma 2) `⁄` corpus 2 (sigma 2) `∕` corpus 2 (sigma 2) `⠀`
`Image`	ends_with	`\cmd.exe` corpus 134 (sigma 134) `\cscript.exe` corpus 76 (sigma 76) `\powershell.exe` corpus 186 (sigma 186) `\powershell_ise.exe` corpus 42 (sigma 42) `\pwsh.exe` corpus 172 (sigma 172) `\wscript.exe` corpus 78 (sigma 78)
`OriginalFileName`	eq	`Cmd.EXE` corpus 65 (sigma 44, splunk 17, elastic 4) `PowerShell.EXE` corpus 121 (sigma 85, splunk 30, elastic 6) `PowerShell_ISE.EXE` corpus 51 (splunk 30, sigma 18, elastic 3) `cscript.exe` corpus 19 (sigma 17, elastic 2) `pwsh.dll` corpus 112 (sigma 79, splunk 30, elastic 3) `wscript.exe` corpus 20 (sigma 17, elastic 3)

`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:`)
`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)

Potential CommandLine Obfuscation Using Unicode Characters From Suspicious Image

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_special_chars`

Indicators

Keyboard shortcuts

Search operators

Potential CommandLine Obfuscation Using Unicode Characters From Suspicious Image

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_special_chars

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_special_chars`