Suspicious WerFault Child Process

Elastic Stack Serverless Security

A suspicious WerFault child process was detected, which may indicate an attempt to run unnoticed. Verify process details such as command line, network connections, file writes and parent process details as well.

Rule type: eql

Rule indices:

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

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://www.hexacorn.com/blog/2019/09/19/silentprocessexit-quick-look-under-the-hood/
• https://github.com/sbousseaden/EVTX-ATTACK-SAMPLES/blob/master/Persistence/persistence_SilentProcessExit_ImageHijack_sysmon_13_1.evtx
• https://web.archive.org/web/20230530011556/https://blog.menasec.net/2021/01/

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Defense Evasion

Version: 5

Rule authors:

• Elastic

Rule license: Elastic License v2

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate event.ingested to @timestamp for this rule to work.

process where event.type in ("start", "process_started") and
  process.parent.name : "WerFault.exe" and
  not process.name : ("cofire.exe",
                      "psr.exe",
                      "VsJITDebugger.exe",
                      "TTTracer.exe",
                      "rundll32.exe",
                      "LogiOptionsMgr.exe") and
  not process.args : ("/LOADSAVEDWINDOWS",
                      "/restore",
                      "RestartByRestartManager*",
                      "--restarted",
                      "createdump",
                      "dontsend",
                      "/watson")

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Defense Evasion
  • ID: TA0005
  • Reference URL: https://attack.mitre.org/tactics/TA0005/

• Technique:

  • Name: Masquerading
  • ID: T1036
  • Reference URL: https://attack.mitre.org/techniques/T1036/