Potential DLL Side-Loading via Microsoft Antimalware Service Executable

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Potential DLL Side-Loading via Microsoft Antimalware Service Executable

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Identifies a Windows trusted program that is known to be vulnerable to DLL Search Order Hijacking starting after being renamed or from a non-standard path. This is uncommon behavior and may indicate an attempt to evade defenses via side-loading a malicious DLL within the memory space of one of those processes.

Rule type: eql

Rule indices:

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

Severity: high

Risk score: 73

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
  • Defense Evasion

Version: 100 (version history)

Added (Elastic Stack release): 7.14.0

Last modified (Elastic Stack release): 8.5.0

Rule authors: Elastic, Dennis Perto

Rule license: Elastic License v2

Potential false positives

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Microsoft Antimalware Service Executable installed on non default installation path.

Investigation guide

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Rule query

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process where event.type == "start" and
(process.pe.original_file_name == "MsMpEng.exe" and not process.name :
"MsMpEng.exe") or (process.name : "MsMpEng.exe" and not
process.executable : ("?:\\ProgramData\\Microsoft\\Windows
Defender\\*.exe", "?:\\Program
Files\\Windows Defender\\*.exe",
"?:\\Program Files (x86)\\Windows Defender\\*.exe",
"?:\\Program Files\\Microsoft Security Client\\*.exe",
"?:\\Program Files (x86)\\Microsoft Security Client\\*.exe"))

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 100 (8.5.0 release)
  • Formatting only
Version 5 (8.4.0 release)
  • Formatting only
Version 3 (8.2.0 release)
  • Formatting only
Version 2 (7.16.0 release)
  • Updated query, changed from:

    process where event.type == "start" and
    (process.pe.original_file_name == "MsMpEng.exe" and not process.name :
    "MsMpEng.exe") or (process.name : "MsMpEng.exe" and not
    process.executable : ("?:\\ProgramData\\Microsoft\\Windows
    Defender\\*.exe", "?:\\Program
    Files\\Windows Defender\\*.exe",
    "?:\\Program Files (x86)\\Windows Defender\\*.exe"))