huntrule

Windows RDP client Mstsc.EXE launched from uncommon browser or email parent process

Alerts when mstsc.exe is spawned by a browser or Outlook, suggesting potential RDP access using a local .rdp file.

FreeUnreviewedSigmahighv1
title: Windows RDP client Mstsc.EXE launched from uncommon browser or email parent process
id: c5665eed-5fbf-4678-bab4-4a319eec25e7
status: test
description: This rule flags process creation where mstsc.exe is launched with an unusual parent process, specifically one of several common web browsers or Outlook. Using mstsc.exe in this context can indicate an attacker attempting RDP connectivity via a local .rdp file placed in a suspicious location. The detection relies on Windows process creation telemetry, matching both the parent image and the executed binary (mstsc.exe) with process path/original filename criteria.
references:
  - https://www.blackhillsinfosec.com/rogue-rdp-revisiting-initial-access-methods/
  - https://web.archive.org/web/20230726144748/https://blog.thickmints.dev/mintsights/detecting-rogue-rdp/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_mstsc_run_local_rpd_file_susp_parent.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2023-04-18
tags:
  - attack.lateral-movement
logsource:
  category: process_creation
  product: windows
detection:
  selection_parent:
    ParentImage|endswith:
      - \brave.exe
      - \CCleanerBrowser.exe
      - \chrome.exe
      - \chromium.exe
      - \firefox.exe
      - \iexplore.exe
      - \microsoftedge.exe
      - \msedge.exe
      - \opera.exe
      - \vivaldi.exe
      - \whale.exe
      - \outlook.exe
  selection_img:
    - Image|endswith: \mstsc.exe
    - OriginalFileName: mstsc.exe
  condition: all of selection_*
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: ff3b6b39-e765-42f9-bb2c-ea6761e0e0f6
    type: derived

What it detects

This rule flags process creation where mstsc.exe is launched with an unusual parent process, specifically one of several common web browsers or Outlook. Using mstsc.exe in this context can indicate an attacker attempting RDP connectivity via a local .rdp file placed in a suspicious location. The detection relies on Windows process creation telemetry, matching both the parent image and the executed binary (mstsc.exe) with process path/original filename criteria.

Known false positives

  • Unlikely

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.