This documentation contains work-in-progress information for future Elastic Stack and Cloud releases. Use the version selector to view supported release docs. It also contains some Elastic Cloud serverless information. Check out our serverless docs for more details.
« Unusual Parent Process for cmd.exe Unusual Persistence via Services Registry »
Elastic Docs ›Elastic Security Solution [8.16] ›Detections and alerts ›Prebuilt rule reference

Unusual Parent-Child Relationship

edit

Unusual Parent-Child Relationship

edit

Identifies Windows programs run from unexpected parent processes. This could indicate masquerading or other strange activity on a system.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*
  • logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Privilege Escalation
  • Investigation Guide

Version: 102 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Investigation guide

edit
## Triage and analysis

### Investigating Unusual Parent-Child Relationship

Windows internal/system processes have some characteristics that can be used to spot suspicious activities. One of these
characteristics is parent-child relationships. These relationships can be used to baseline the typical behavior of the
system and then alert on occurrences that don't comply with the baseline.

This rule uses this information to spot suspicious parent and child processes.

> **Note**:
> This investigation guide uses the [Osquery Markdown Plugin]({security-guide}/invest-guide-run-osquery.html) introduced in Elastic stack version 8.5.0. Older Elastic stacks versions will see unrendered markdown in this guide.

#### Possible investigation steps

- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files
for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications,
and any spawned child processes.
- Examine the host for derived artifacts that indicates suspicious activities:
  - Analyze the process executable using a private sandboxed analysis system.
  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
    - Attempts to contact external domains and addresses.
      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by
      filtering by the process' `process.entity_id`.
      - Examine the DNS cache for suspicious or anomalous entries.
        - !{osquery{"query":"SELECT * FROM dns_cache", "label":"Osquery - Retrieve DNS Cache"}}
    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related
    processes in the process tree.
    - Examine the host services for suspicious or anomalous entries.
      - !{osquery{"query":"SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services","label":"Osquery - Retrieve All Services"}}
      - !{osquery{"query":"SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services WHERE NOT (user_account LIKE "%LocalSystem" OR user_account LIKE "%LocalService" OR user_account LIKE "%NetworkService" OR user_account == null)","label":"Osquery - Retrieve Services Running on User Accounts"}}
      - !{osquery{"query":"SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, name, description, start_type, status, pid, services.path FROM services JOIN authenticode ON services.path = authenticode.path OR services.module_path = authenticode.path JOIN hash ON services.path = hash.path WHERE authenticode.result != "trusted"","label":"Osquery - Retrieve Service Unsigned Executables with Virustotal Link"}}
  - Retrieve the files' SHA-256 hash values using the PowerShell `Get-FileHash` cmdlet and search for the existence and
  reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.


### False positive analysis

- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved host to prevent further post-compromise behavior.
- If the triage identified malware, search the environment for additional compromised hosts.
  - Implement temporary network rules, procedures, and segmentation to contain the malware.
  - Stop suspicious processes.
  - Immediately block the identified indicators of compromise (IoCs).
  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that
  attackers could use to reinfect the system.
- Remove and block malicious artifacts identified during triage.
- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
malware components.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
mean time to respond (MTTR).

Rule query

edit
process where event.type == "start" and process.parent.name != null
and ( /* suspicious parent processes */
(process.name:"autochk.exe" and not process.parent.name:"smss.exe") or
(process.name:("fontdrvhost.exe", "dwm.exe") and not
process.parent.name:("wininit.exe", "winlogon.exe")) or
(process.name:("consent.exe", "RuntimeBroker.exe", "TiWorker.exe") and
not process.parent.name:"svchost.exe") or
(process.name:"SearchIndexer.exe" and not
process.parent.name:"services.exe") or
(process.name:"SearchProtocolHost.exe" and not
process.parent.name:("SearchIndexer.exe", "dllhost.exe")) or
(process.name:"dllhost.exe" and not
process.parent.name:("services.exe", "svchost.exe")) or
(process.name:"smss.exe" and not process.parent.name:("System",
"smss.exe")) or (process.name:"csrss.exe" and not
process.parent.name:("smss.exe", "svchost.exe")) or
(process.name:"wininit.exe" and not process.parent.name:"smss.exe") or
(process.name:"winlogon.exe" and not process.parent.name:"smss.exe")
or (process.name:("lsass.exe", "LsaIso.exe") and not
process.parent.name:"wininit.exe") or (process.name:"LogonUI.exe"
and not process.parent.name:("wininit.exe", "winlogon.exe")) or
(process.name:"services.exe" and not
process.parent.name:"wininit.exe") or (process.name:"svchost.exe"
and not process.parent.name:("MsMpEng.exe", "services.exe")) or
(process.name:"spoolsv.exe" and not
process.parent.name:"services.exe") or (process.name:"taskhost.exe"
and not process.parent.name:("services.exe", "svchost.exe")) or
(process.name:"taskhostw.exe" and not
process.parent.name:("services.exe", "svchost.exe")) or
(process.name:"userinit.exe" and not process.parent.name:("dwm.exe",
"winlogon.exe")) or (process.name:("wmiprvse.exe",
"wsmprovhost.exe", "winrshost.exe") and not
process.parent.name:"svchost.exe") or /* suspicious child processes
*/ (process.parent.name:("SearchProtocolHost.exe", "taskhost.exe",
"csrss.exe") and not process.name:("werfault.exe", "wermgr.exe",
"WerFaultSecure.exe")) or (process.parent.name:"autochk.exe" and
not process.name:("chkdsk.exe", "doskey.exe", "WerFault.exe")) or
(process.parent.name:"smss.exe" and not process.name:("autochk.exe",
"smss.exe", "csrss.exe", "wininit.exe", "winlogon.exe", "setupcl.exe",
"WerFault.exe")) or (process.parent.name:"wermgr.exe" and not
process.name:("WerFaultSecure.exe", "wermgr.exe", "WerFault.exe")) or
(process.parent.name:"conhost.exe" and not
process.name:("mscorsvw.exe", "wermgr.exe", "WerFault.exe",
"WerFaultSecure.exe")) )

Threat mapping

edit

Framework: MITRE ATT&CKTM

Rule version history

edit
Version 102 (8.6.0 release)
  • Formatting only
Version 101 (8.5.0 release)

  • Updated query, changed from:

    process where event.type in ("start", "process_started") and
process.parent.name != null and ( /* suspicious parent processes
*/ (process.name:"autochk.exe" and not
process.parent.name:"smss.exe") or
(process.name:("fontdrvhost.exe", "dwm.exe") and not
process.parent.name:("wininit.exe", "winlogon.exe")) or
(process.name:("consent.exe", "RuntimeBroker.exe", "TiWorker.exe") and
not process.parent.name:"svchost.exe") or
(process.name:"SearchIndexer.exe" and not
process.parent.name:"services.exe") or
(process.name:"SearchProtocolHost.exe" and not
process.parent.name:("SearchIndexer.exe", "dllhost.exe")) or
(process.name:"dllhost.exe" and not
process.parent.name:("services.exe", "svchost.exe")) or
(process.name:"smss.exe" and not process.parent.name:("System",
"smss.exe")) or (process.name:"csrss.exe" and not
process.parent.name:("smss.exe", "svchost.exe")) or
(process.name:"wininit.exe" and not process.parent.name:"smss.exe") or
(process.name:"winlogon.exe" and not process.parent.name:"smss.exe")
or (process.name:("lsass.exe", "LsaIso.exe") and not
process.parent.name:"wininit.exe") or (process.name:"LogonUI.exe"
and not process.parent.name:("wininit.exe", "winlogon.exe")) or
(process.name:"services.exe" and not
process.parent.name:"wininit.exe") or (process.name:"svchost.exe"
and not process.parent.name:("MsMpEng.exe", "services.exe")) or
(process.name:"spoolsv.exe" and not
process.parent.name:"services.exe") or (process.name:"taskhost.exe"
and not process.parent.name:("services.exe", "svchost.exe")) or
(process.name:"taskhostw.exe" and not
process.parent.name:("services.exe", "svchost.exe")) or
(process.name:"userinit.exe" and not process.parent.name:("dwm.exe",
"winlogon.exe")) or (process.name:("wmiprvse.exe",
"wsmprovhost.exe", "winrshost.exe") and not
process.parent.name:"svchost.exe") or /* suspicious child processes
*/ (process.parent.name:("SearchProtocolHost.exe", "taskhost.exe",
"csrss.exe") and not process.name:("werfault.exe", "wermgr.exe",
"WerFaultSecure.exe")) or (process.parent.name:"autochk.exe" and
not process.name:("chkdsk.exe", "doskey.exe", "WerFault.exe")) or
(process.parent.name:"smss.exe" and not process.name:("autochk.exe",
"smss.exe", "csrss.exe", "wininit.exe", "winlogon.exe", "setupcl.exe",
"WerFault.exe")) or (process.parent.name:"wermgr.exe" and not
process.name:("WerFaultSecure.exe", "wermgr.exe", "WerFault.exe")) or
(process.parent.name:"conhost.exe" and not
process.name:("mscorsvw.exe", "wermgr.exe", "WerFault.exe",
"WerFaultSecure.exe")) )
Version 13 (8.4.0 release)
  • Formatting only
Version 11 (8.2.0 release)
  • Formatting only
Version 10 (7.16.0 release)
  • Formatting only
Version 9 (7.15.0 release)
  • Formatting only
Version 8 (7.12.0 release)
  • Formatting only
Version 7 (7.11.2 release)
  • Formatting only
Version 6 (7.11.0 release)

  • Updated query, changed from:

    event.category:process and event.type:(start or process_started) and
process.parent.executable:* and (process.parent.name:autochk.exe and
not process.name:(chkdsk.exe or doskey.exe or WerFault.exe) or
process.parent.name:smss.exe and not process.name:(autochk.exe or
smss.exe or csrss.exe or wininit.exe or winlogon.exe or WerFault.exe)
or process.name:autochk.exe and not process.parent.name:smss.exe or
process.name:(fontdrvhost.exe or dwm.exe) and not
process.parent.name:(wininit.exe or winlogon.exe) or
process.name:(consent.exe or RuntimeBroker.exe or TiWorker.exe) and
not process.parent.name:svchost.exe or process.name:wermgr.exe and not
process.parent.name:(svchost.exe or TiWorker.exe) or
process.name:SearchIndexer.exe and not
process.parent.name:services.exe or
process.name:SearchProtocolHost.exe and not
process.parent.name:(SearchIndexer.exe or dllhost.exe) or
process.name:dllhost.exe and not process.parent.name:(services.exe or
svchost.exe) or process.name:smss.exe and not
process.parent.name:(System or smss.exe) or process.name:csrss.exe and
not process.parent.name:(smss.exe or svchost.exe) or
process.name:wininit.exe and not process.parent.name:smss.exe or
process.name:winlogon.exe and not process.parent.name:smss.exe or
process.name:(lsass.exe or LsaIso.exe) and not
process.parent.name:wininit.exe or process.name:LogonUI.exe and not
process.parent.name:(wininit.exe or winlogon.exe) or
process.name:services.exe and not process.parent.name:wininit.exe or
process.name:svchost.exe and not process.parent.name:(MsMpEng.exe or
services.exe) or process.name:spoolsv.exe and not
process.parent.name:services.exe or process.name:taskhost.exe and not
process.parent.name:(services.exe or svchost.exe) or
process.name:taskhostw.exe and not process.parent.name:(services.exe
or svchost.exe) or process.name:userinit.exe and not
process.parent.name:(dwm.exe or winlogon.exe))
Version 5 (7.10.0 release)

  • Updated query, changed from:

    event.category:process and event.type:(start or process_started) and
process.parent.executable:* and (process.name:smss.exe and not
process.parent.name:(System or smss.exe) or process.name:csrss.exe and
not process.parent.name:(smss.exe or svchost.exe) or
process.name:wininit.exe and not process.parent.name:smss.exe or
process.name:winlogon.exe and not process.parent.name:smss.exe or
process.name:lsass.exe and not process.parent.name:wininit.exe or
process.name:LogonUI.exe and not process.parent.name:(wininit.exe or
winlogon.exe) or process.name:services.exe and not
process.parent.name:wininit.exe or process.name:svchost.exe and not
process.parent.name:(MsMpEng.exe or services.exe) or
process.name:spoolsv.exe and not process.parent.name:services.exe or
process.name:taskhost.exe and not process.parent.name:(services.exe or
svchost.exe) or process.name:taskhostw.exe and not
process.parent.name:(services.exe or svchost.exe) or
process.name:userinit.exe and not process.parent.name:(dwm.exe or
winlogon.exe))
Version 4 (7.9.1 release)
  • Formatting only
Version 3 (7.9.0 release)

  • Updated query, changed from:

    event.action:"Process Create (rule: ProcessCreate)" and
process.parent.executable:* and (process.name:smss.exe and not
process.parent.name:(System or smss.exe) or process.name:csrss.exe and
not process.parent.name:(smss.exe or svchost.exe) or
process.name:wininit.exe and not process.parent.name:smss.exe or
process.name:winlogon.exe and not process.parent.name:smss.exe or
process.name:lsass.exe and not process.parent.name:wininit.exe or
process.name:LogonUI.exe and not process.parent.name:(wininit.exe or
winlogon.exe) or process.name:services.exe and not
process.parent.name:wininit.exe or process.name:svchost.exe and not
process.parent.name:(MsMpEng.exe or services.exe) or
process.name:spoolsv.exe and not process.parent.name:services.exe or
process.name:taskhost.exe and not process.parent.name:(services.exe or
svchost.exe) or process.name:taskhostw.exe and not
process.parent.name:(services.exe or svchost.exe) or
process.name:userinit.exe and not process.parent.name:(dwm.exe or
winlogon.exe))
Version 2 (7.7.0 release)

  • Updated query, changed from:

    event.action:"Process Create (rule: ProcessCreate)" and
process.parent.executable:* and ( (process.name:"smss.exe" and not
process.parent.name:("System" or "smss.exe")) or
(process.name:"csrss.exe" and not process.parent.name:("smss.exe" or
"svchost.exe")) or (process.name:"wininit.exe" and not
process.parent.name:"smss.exe") or (process.name:"winlogon.exe" and
not process.parent.name:"smss.exe") or (process.name:"lsass.exe" and
not process.parent.name:"wininit.exe") or (process.name:"LogonUI.exe"
and not process.parent.name:("winlogon.exe" or "wininit.exe")) or
(process.name:"services.exe" and not
process.parent.name:"wininit.exe") or (process.name:"svchost.exe" and
not process.parent.name:("services.exe" or "MsMpEng.exe")) or
(process.name:"spoolsv.exe" and not
process.parent.name:"services.exe") or (process.name:"taskhost.exe"
and not process.parent.name:("services.exe" or "svchost.exe")) or
(process.name:"taskhostw.exe" and not
process.parent.name:("services.exe" or "svchost.exe")) or
(process.name:"userinit.exe" and not process.parent.name:("dwm.exe" or
"winlogon.exe")) )
« Unusual Parent Process for cmd.exe Unusual Persistence via Services Registry »