Process Activity via Compiled HTML File

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Compiled HTML files (.chm) are commonly distributed as part of the Microsoft HTML Help system. Adversaries may conceal malicious code in a CHM file and deliver it to a victim for execution. CHM content is loaded by the HTML Help executable program (hh.exe).

Rule type: query

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*
  • logs-windows.*

Severity: low

Risk score: 21

Runs every: 5 minutes

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

Maximum alerts per execution: 100

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Execution

Version: 7 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.12.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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The HTML Help executable program (hh.exe) runs whenever a user clicks a compiled help (.chm) file or menu item that opens the help file inside the Help Viewer. This is not always malicious, but adversaries may abuse this technology to conceal malicious code.

Rule query

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event.category:process and event.type:(start or process_started) and
process.name:hh.exe

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 7 (7.12.0 release)
  • Formatting only
Version 6 (7.11.2 release)
  • Formatting only
Version 5 (7.11.0 release)
  • Formatting only
Version 4 (7.10.0 release)
  • Updated query, changed from:

    event.code:1 and process.name:hh.exe
Version 3 (7.9.0 release)
  • Formatting only
Version 2 (7.7.0 release)
  • Formatting only