VMToolsd Suspicious Child Process

Status: test
Severity: high
Log source: product windows, category process_creation
Author: bohops, Bhabesh Raj
Source: github.com/SigmaHQ/sigma

Detects suspicious child process creations of VMware Tools process which may indicate persistence setup

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059` Command and Scripting Interpreter

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: VMToolsd Suspicious Child Process
id: 5687f942-867b-4578-ade7-1e341c46e99a
status: test
description: Detects suspicious child process creations of VMware Tools process which may indicate persistence setup
references:
    - https://bohops.com/2021/10/08/analyzing-and-detecting-a-vmtools-persistence-technique/
    - https://user-images.githubusercontent.com/61026070/136518004-b68cce7d-f9b8-4e9a-9b7b-53b1568a9a94.png
    - https://github.com/vmware/open-vm-tools/blob/master/open-vm-tools/tools.conf
author: bohops, Bhabesh Raj
date: 2021-10-08
modified: 2023-07-25
tags:
    - attack.execution
    - attack.persistence
    - attack.t1059
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\vmtoolsd.exe'
    selection_img:
        - Image|endswith:
              - '\cmd.exe'
              - '\cscript.exe'
              - '\mshta.exe'
              - '\powershell.exe'
              - '\pwsh.exe'
              - '\regsvr32.exe'
              - '\rundll32.exe'
              - '\wscript.exe'
        - OriginalFileName:
              - 'Cmd.Exe'
              - 'cscript.exe'
              - 'MSHTA.EXE'
              - 'PowerShell.EXE'
              - 'pwsh.dll'
              - 'REGSVR32.EXE'
              - 'RUNDLL32.EXE'
              - 'wscript.exe'
    filter_main_vmwaretools_script:
        Image|endswith: '\cmd.exe'
        CommandLine|contains:
            - '\VMware\VMware Tools\poweron-vm-default.bat'
            - '\VMware\VMware Tools\poweroff-vm-default.bat'
            - '\VMware\VMware Tools\resume-vm-default.bat'
            - '\VMware\VMware Tools\suspend-vm-default.bat'
    filter_main_empty:
        Image|endswith: '\cmd.exe'
        CommandLine: ''
    filter_main_null:
        Image|endswith: '\cmd.exe'
        CommandLine: null
    condition: all of selection* and not 1 of filter_main_*
falsepositives:
    - Legitimate use by VM administrator
level: high

Stages and Predicates

Stage 0: `condition`

all of selection* and not 1 of filter_main_*

Stage 1: `selection_parent`

selection_parent:
    ParentImage|endswith: '\vmtoolsd.exe'

Stage 2: `selection_img`

selection_img:
    - Image|endswith:
          - '\cmd.exe'
          - '\cscript.exe'
          - '\mshta.exe'
          - '\powershell.exe'
          - '\pwsh.exe'
          - '\regsvr32.exe'
          - '\rundll32.exe'
          - '\wscript.exe'
    - OriginalFileName:
          - 'Cmd.Exe'
          - 'cscript.exe'
          - 'MSHTA.EXE'
          - 'PowerShell.EXE'
          - 'pwsh.dll'
          - 'REGSVR32.EXE'
          - 'RUNDLL32.EXE'
          - 'wscript.exe'

Stage 3: `not filter_main_*`

filter_main_vmwaretools_script:
    Image|endswith: '\cmd.exe'
    CommandLine|contains:
        - '\VMware\VMware Tools\poweron-vm-default.bat'
        - '\VMware\VMware Tools\poweroff-vm-default.bat'
        - '\VMware\VMware Tools\resume-vm-default.bat'
        - '\VMware\VMware Tools\suspend-vm-default.bat'
filter_main_empty:
    Image|endswith: '\cmd.exe'
    CommandLine: ''
filter_main_null:
    Image|endswith: '\cmd.exe'
    CommandLine: null

Exclusions

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

Field	Kind	Excluded values
`CommandLine`	match	`\VMware\VMware Tools\poweroff-vm-default.bat`
`CommandLine`	match	`\VMware\VMware Tools\poweron-vm-default.bat`
`CommandLine`	match	`\VMware\VMware Tools\resume-vm-default.bat`
`CommandLine`	match	`\VMware\VMware Tools\suspend-vm-default.bat`
`Image`	ends_with	`\cmd.exe`
`Image`	ends_with	`\cmd.exe`
`CommandLine`	is_null	(no value, null check)
`Image`	ends_with	`\cmd.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`	ends_with	`\cmd.exe` corpus 130 (sigma 130) `\cscript.exe` corpus 73 (sigma 73) `\mshta.exe` corpus 67 (sigma 67) `\powershell.exe` corpus 182 (sigma 182) `\pwsh.exe` corpus 168 (sigma 168) `\regsvr32.exe` corpus 65 (sigma 65) `\rundll32.exe` corpus 95 (sigma 95) `\wscript.exe` corpus 75 (sigma 75)
`OriginalFileName`	eq	`Cmd.Exe` corpus 65 (sigma 43, splunk 17, elastic 5) `MSHTA.EXE` corpus 22 (sigma 13, splunk 6, elastic 3) `PowerShell.EXE` corpus 120 (sigma 84, splunk 30, elastic 6) `REGSVR32.EXE` corpus 26 (sigma 17, splunk 6, elastic 3) `RUNDLL32.EXE` corpus 62 (sigma 35, splunk 21, elastic 6) `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)
`ParentImage`	ends_with	`\vmtoolsd.exe`

`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)

VMToolsd Suspicious Child Process

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_parent`

Stage 2: `selection_img`

Stage 3: `not filter_main_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

VMToolsd Suspicious Child Process

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_parent

Stage 2: selection_img

Stage 3: not filter_main_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_parent`

Stage 2: `selection_img`

Stage 3: `not filter_main_*`