Potential DLL Side-Loading via Trusted Microsoft Programs

Identifies an instance of 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.process-*
logs-windows.sysmon_operational-*
endgame-*
logs-m365_defender.event-*

Severity: high

Risk score: 73

Runs every: 5m

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

Maximum alerts per execution: 100

References: None

Tags:

Domain: Endpoint
OS: Windows
Use Case: Threat Detection
Tactic: Defense Evasion
Tactic: Execution
Data Source: Elastic Endgame
Data Source: Elastic Defend
Data Source: Sysmon
Data Source: Microsoft Defender for Endpoint

Version: 211

Rule authors:

Elastic

Rule license: Elastic License v2

Setup

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Setup

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 version 8.2. Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate event.ingested to @timestamp. For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html

Rule query

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process where host.os.type == "windows" and event.type == "start" and
  process.pe.original_file_name in ("WinWord.exe", "EXPLORER.EXE", "w3wp.exe", "DISM.EXE") and
  not (process.name : ("winword.exe", "explorer.exe", "w3wp.exe", "Dism.exe") or
         process.executable : ("?:\\Windows\\explorer.exe",
                               "?:\\Program Files\\Microsoft Office\\root\\Office*\\WINWORD.EXE",
                               "?:\\Program Files?(x86)\\Microsoft Office\\root\\Office*\\WINWORD.EXE",
                               "?:\\Windows\\System32\\Dism.exe",
                               "?:\\Windows\\SysWOW64\\Dism.exe",
                               "?:\\Windows\\System32\\inetsrv\\w3wp.exe")
         )

Framework: MITRE ATT&CK^TM

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/
Technique:
- Name: Hijack Execution Flow
- ID: T1574
- Reference URL: https://attack.mitre.org/techniques/T1574/
Sub-technique:
- Name: DLL Side-Loading
- ID: T1574.002
- Reference URL: https://attack.mitre.org/techniques/T1574/002/

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