Suspicious Child Process of SolarWinds WebHelpDesk

Status: experimental
Severity: high
Log source: product windows, category process_creation
Author: Huntress Team, Swachchhanda Shrawan Poudel (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects suspicious child processes spawned by SolarWinds WebHelpDesk (WHD) application, which may indicate exploitation activity leveraging RCE vulnerabilities such as CVE-2025-40551, CVE-2025-40536, or CVE-2025-26399

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Suspicious Child Process of SolarWinds WebHelpDesk
id: 8c7f4a2d-3b9e-4f1c-9a6d-2e8f5c3d9a1b
status: experimental
description: |
    Detects suspicious child processes spawned by SolarWinds WebHelpDesk (WHD) application, which may indicate exploitation activity leveraging RCE vulnerabilities such as CVE-2025-40551, CVE-2025-40536, or CVE-2025-26399
references:
    - https://www.microsoft.com/en-us/security/blog/2026/02/06/active-exploitation-solarwinds-web-help-desk/
    - https://www.huntress.com/blog/active-exploitation-solarwinds-web-help-desk-cve-2025-26399
    - https://documentation.solarwinds.com/en/success_center/whd/content/release_notes/whd_2026-1_release_notes.htm
author: Huntress Team, Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2026-02-11
tags:
    - attack.initial-access
    - attack.t1190
    - cve.2025-26399
    - cve.2025-40536
    - cve.2025-40551
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|contains: '\WebHelpDesk\bin\'
        ParentImage|endswith:
            - '\java.exe'
            - '\javaw.exe'
        ParentCommandLine|contains: 'tomcat'
    selection_suspicious_child:
        CommandLine|contains:
            - '-enc'
            - 'base64'
            - 'bitsadmin'
            - 'certutil'
            - 'curl'
            - 'Invoke-RestMethod'
            - 'Invoke-WebRequest'
            - 'irm '
            - 'iwr '
            - 'mshta'
            - 'msiexec'
            - 'Net.WebClient'
            - 'Start-BitsTransfer'
            - 'wget'
            - 'wmic'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_parent`

selection_parent:
    ParentImage|contains: '\WebHelpDesk\bin\'
    ParentImage|endswith:
        - '\java.exe'
        - '\javaw.exe'
    ParentCommandLine|contains: 'tomcat'

Stage 2: `selection_suspicious_child`

selection_suspicious_child:
    CommandLine|contains:
        - '-enc'
        - 'base64'
        - 'bitsadmin'
        - 'certutil'
        - 'curl'
        - 'Invoke-RestMethod'
        - 'Invoke-WebRequest'
        - 'irm '
        - 'iwr '
        - 'mshta'
        - 'msiexec'
        - 'Net.WebClient'
        - 'Start-BitsTransfer'
        - 'wget'
        - 'wmic'

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	`-enc` corpus 2 (sigma 2) `Invoke-RestMethod` corpus 5 (sigma 5) `Invoke-WebRequest` corpus 13 (sigma 10, elastic 1, chronicle 1, kusto 1) `Net.WebClient` corpus 2 (sigma 2) `Start-BitsTransfer` corpus 4 (sigma 3, splunk 1) `base64` corpus 11 (sigma 7, elastic 4) `bitsadmin` corpus 10 (sigma 10) `certutil` corpus 12 (sigma 10, kusto 2) `curl` corpus 17 (sigma 14, elastic 2, splunk 1) `irm` corpus 5 (sigma 5) `iwr` corpus 13 (sigma 11, chronicle 2) `mshta` corpus 14 (sigma 14) `msiexec` corpus 5 (sigma 5) `wget` corpus 11 (sigma 8, elastic 1, splunk 1, kusto 1) `wmic` corpus 6 (sigma 6)
`ParentCommandLine`	match	`tomcat` corpus 2 (sigma 2)
`ParentImage`	ends_with	`\java.exe` corpus 8 (sigma 8) `\javaw.exe` corpus 7 (sigma 7)
`ParentImage`	match	`\WebHelpDesk\bin\`

`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)

Suspicious Child Process of SolarWinds WebHelpDesk

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_parent`

Stage 2: `selection_suspicious_child`

Indicators

Keyboard shortcuts

Search operators

Suspicious Child Process of SolarWinds WebHelpDesk

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_parent

Stage 2: selection_suspicious_child

Indicators

Stage 0: `condition`

Stage 1: `selection_parent`

Stage 2: `selection_suspicious_child`