Suspicious WerFault Child Process

Elastic Stack Serverless Security

A suspicious WerFault child process was detected, which may indicate an attempt to run via the SilentProcessExit registry key manipulation. Verify process details such as command line, network connections and file writes.

Rule type: eql

Rule indices:

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

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://www.hexacorn.com/blog/2019/09/20/werfault-command-line-switches-v0-1/
• 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
• Elastic Endgame

Version: 104

Rule authors:

• Elastic

Rule license: Elastic License v2

process where event.type == "start" and

  process.parent.name : "WerFault.exe" and

  /* args -s and -t used to execute a process via SilentProcessExit mechanism */
  (process.parent.args : "-s" and process.parent.args : "-t" and process.parent.args : "-c") and

  not process.executable : ("?:\\Windows\\SysWOW64\\Initcrypt.exe", "?:\\Program Files (x86)\\Heimdal\\Heimdal.Guard.exe")

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/