Use NTFS Short Name in Image

Status: test
Severity: medium
Log source: product windows, category process_creation
Author: frack113, Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detect use of the Windows 8.3 short name. Which could be used as a method to avoid Image based detection

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1564.004` Hide Artifacts: NTFS File Attributes

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: Use NTFS Short Name in Image
id: 3ef5605c-9eb9-47b0-9a71-b727e6aa5c3b
related:
    - id: dd6b39d9-d9be-4a3b-8fe0-fe3c6a5c1795
      type: similar
status: test
description: Detect use of the Windows 8.3 short name. Which could be used as a method to avoid Image based detection
references:
    - https://www.acunetix.com/blog/articles/windows-short-8-3-filenames-web-security-problem/
    - https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-2000-server/cc959352(v=technet.10)
    - https://twitter.com/jonasLyk/status/1555914501802921984
author: frack113, Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-06
modified: 2023-07-20
tags:
    - attack.stealth
    - attack.t1564.004
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|contains:
            - '~1.bat'
            - '~1.dll'
            - '~1.exe'
            - '~1.hta'
            - '~1.js'
            - '~1.msi'
            - '~1.ps1'
            - '~1.tmp'
            - '~1.vbe'
            - '~1.vbs'
            - '~2.bat'
            - '~2.dll'
            - '~2.exe'
            - '~2.hta'
            - '~2.js'
            - '~2.msi'
            - '~2.ps1'
            - '~2.tmp'
            - '~2.vbe'
            - '~2.vbs'
    filter_main_generic_parent:
        ParentImage: 'C:\Windows\explorer.exe'
    filter_optional_webex:
        ParentImage|endswith: '\WebEx\WebexHost.exe'
    filter_optional_thor:
        ParentImage|endswith: '\thor\thor64.exe'
    filter_optional_winzip:
        Image: 'C:\PROGRA~1\WinZip\WZPREL~1.EXE'
    filter_optional_vcred:
        Image|endswith: '\VCREDI~1.EXE'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Software Installers
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection`

selection:
    Image|contains:
        - '~1.bat'
        - '~1.dll'
        - '~1.exe'
        - '~1.hta'
        - '~1.js'
        - '~1.msi'
        - '~1.ps1'
        - '~1.tmp'
        - '~1.vbe'
        - '~1.vbs'
        - '~2.bat'
        - '~2.dll'
        - '~2.exe'
        - '~2.hta'
        - '~2.js'
        - '~2.msi'
        - '~2.ps1'
        - '~2.tmp'
        - '~2.vbe'
        - '~2.vbs'

Stage 2: `not filter_main_generic_parent`

filter_main_generic_parent:
    ParentImage: 'C:\Windows\explorer.exe'

Stage 3: `not filter_optional_*`

filter_optional_webex:
    ParentImage|endswith: '\WebEx\WebexHost.exe'
filter_optional_thor:
    ParentImage|endswith: '\thor\thor64.exe'
filter_optional_winzip:
    Image: 'C:\PROGRA~1\WinZip\WZPREL~1.EXE'
filter_optional_vcred:
    Image|endswith: '\VCREDI~1.EXE'

Exclusions

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

Field	Kind	Excluded values
`ParentImage`	eq	`C:\Windows\explorer.exe`
`Image`	ends_with	`\VCREDI~1.EXE`
`Image`	eq	`C:\PROGRA~1\WinZip\WZPREL~1.EXE`
`ParentImage`	ends_with	`\WebEx\WebexHost.exe`
`ParentImage`	ends_with	`\thor\thor64.exe`

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
`Image`	match	`~1.bat` `~1.dll` `~1.exe` `~1.hta` `~1.js` `~1.msi` `~1.ps1` `~1.tmp` `~1.vbe` `~1.vbs` `~2.bat` `~2.dll` `~2.exe` `~2.hta` `~2.js` `~2.msi` `~2.ps1` `~2.tmp` `~2.vbe` `~2.vbs`

`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)

Use NTFS Short Name in Image

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_generic_parent`

Stage 3: `not filter_optional_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Use NTFS Short Name in Image

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_main_generic_parent

Stage 3: not filter_optional_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_generic_parent`

Stage 3: `not filter_optional_*`