Suspicious Outlook Child Process

Identifies suspicious child processes spawned by MS Outlook, which can indicate a potential masquerading or the exploitation of a vulnerability on the application causing it to execute code.

Rule type: eql

Rule indices:

logs-endpoint.events.process-*

Severity: low

Risk score: 21

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: Persistence
Rule Type: BBR
Data Source: Elastic Defend

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

process where host.os.type == "windows" and event.type == "start" and
  process.parent.name : "outlook.exe" and
  not (
    (
      process.executable : (
        "?:\\Program Files\\*",
        "?:\\Program Files (x86)\\*",
        "?:\\Windows\\System32\\WerFault.exe",
        "?:\\Windows\\SysWOW64\\WerFault.exe",
        "?:\\Windows\\system32\\wermgr.exe",
        "?:\\Users\\*\\AppData\\Local\\Microsoft\\Teams\\current\\Teams.exe",
        "?:\\Users\\*\\AppData\\Local\\Temp\\NewOutlookInstall\\NewOutlookInstaller.exe",
        "?:\\Users\\*\\AppData\\Local\\Google\\Chrome\\Application\\chrome.exe",
        "?:\\Users\\*\\AppData\\Local\\Island\\Island\\Application\\Island.exe",
        "?:\\Users\\*\\AppData\\Local\\Mozilla Firefox\\firefox.exe",
        "?:\\Users\\*\\AppData\\Roaming\\Zoom\\bin\\Zoom.exe",
        "?:\\Windows\\System32\\IME\\SHARED\\IMEWDBLD.EXE",
        "?:\\Windows\\System32\\spool\\drivers\\x64\\*",
        "?:\\Windows\\System32\\prevhost.exe",
        "?:\\Windows\\System32\\dwwin.exe",
        "?:\\Windows\\System32\\mspaint.exe",
        "?:\\Windows\\SysWOW64\\mspaint.exe",
        "?:\\Windows\\System32\\notepad.exe",
        "?:\\Windows\\SysWOW64\\notepad.exe",
        "?:\\Windows\\System32\\smartscreen.exe",
        "?:\\Windows\\explorer.exe",
        "?:\\Windows\\splwow64.exe"
      ) and process.code_signature.trusted == true
    ) or
    (
      process.name : "rundll32.exe" and
      process.args : "*hpmsn???.dll,MonitorPrintJobStatus*"
    )
  )

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/
Sub-technique:
- Name: Invalid Code Signature
- ID: T1036.001
- Reference URL: https://attack.mitre.org/techniques/T1036/001/
Sub-technique:
- Name: Match Legitimate Name or Location
- ID: T1036.005
- Reference URL: https://attack.mitre.org/techniques/T1036/005/
Technique:
- Name: Process Injection
- ID: T1055
- Reference URL: https://attack.mitre.org/techniques/T1055/
Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Compromise Host Software Binary
- ID: T1554
- Reference URL: https://attack.mitre.org/techniques/T1554/

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