Suspicious RDP ActiveX Client Loaded

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Identifies suspicious Image Loading of the Remote Desktop Services ActiveX Client (mstscax), this may indicate the presence of RDP lateral movement capability.

Rule type: eql

Rule indices:

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

Severity: medium

Risk score: 47

Runs every: 5m

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

Maximum alerts per execution: 100

References:

Tags:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Lateral Movement
  • Data Source: Elastic Endgame
  • Data Source: Elastic Defend
  • Data Source: Sysmon

Version: 109

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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any where host.os.type == "windows" and
 (event.category : ("library", "driver") or (event.category == "process" and event.action : "Image loaded*")) and
 (?dll.name : "mstscax.dll" or file.name : "mstscax.dll") and
   /* depending on noise in your env add here extra paths  */
  process.executable : (
    "C:\\Windows\\*",
    "C:\\Users\\Public\\*",
    "C:\\Users\\Default\\*",
    "C:\\Intel\\*",
    "C:\\PerfLogs\\*",
    "C:\\ProgramData\\*",
    "\\Device\\Mup\\*",
    "\\\\*"
  ) and
  /* add here FPs */
  not process.executable : (
    "?:\\Windows\\System32\\mstsc.exe",
    "?:\\Windows\\SysWOW64\\mstsc.exe",
    "?:\\Windows\\System32\\vmconnect.exe",
    "?:\\Windows\\System32\\WindowsSandboxClient.exe",
    "?:\\Windows\\System32\\hvsirdpclient.exe"
  )

Framework: MITRE ATT&CKTM