Script Execution via Microsoft HTML Application

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Script Execution via Microsoft HTML Application

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Identifies the execution of scripts via HTML applications using Windows utilities rundll32.exe or mshta.exe. Adversaries may bypass process and/or signature-based defenses by proxying execution of malicious content with signed binaries.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-windows.*
  • logs-system.security*
  • logs-windows.sysmon_operational-*
  • logs-sentinel_one_cloud_funnel.*
  • 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
  • Data Source: System
  • Data Source: Sysmon
  • Data Source: SentinelOne
  • Data Source: Microsoft Defender for Endpoint

Version: 201

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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process where host.os.type == "windows" and event.type == "start" and
 process.name : ("rundll32.exe", "mshta.exe") and
  (
     (process.command_line :
        (
        "*script*eval(*",
         "*script*GetObject*",
         "*.regread(*",
         "*WScript.Shell*",
         "*.run(*",
         "*).Exec()*",
         "*mshta*http*",
         "*mshtml*RunHTMLApplication*",
         "*mshtml*,#135*",
         "*StrReverse*",
         "*.RegWrite*",
         /* Issue #379 */
         "*window.close(*",
         "* Chr(*"
         )
     and not process.parent.executable :
                  ("?:\\Program Files (x86)\\Citrix\\System32\\wfshell.exe",
                   "?:\\Program Files (x86)\\Microsoft Office\\Office*\\MSACCESS.EXE",
                   "?:\\Program Files\\Quokka.Works GTInstaller\\GTInstaller.exe")
     ) or

    (process.name : "mshta.exe" and
     not process.command_line : ("*.hta*", "*.htm*", "-Embedding") and process.args_count >=2) or

     /* Execution of HTA file downloaded from the internet */
     (process.name : "mshta.exe" and process.command_line : "*\\Users\\*\\Downloads\\*.hta*") or

     /* Execution of HTA file from archive */
     (process.name : "mshta.exe" and
      process.args : ("?:\\Users\\*\\Temp\\7z*", "?:\\Users\\*\\Temp\\Rar$*", "?:\\Users\\*\\Temp\\Temp?_*", "?:\\Users\\*\\Temp\\BNZ.*"))
   )

Framework: MITRE ATT&CKTM