name: Detect HTML Help Renamed
id: 62fed254-513b-460e-953d-79771493a9f3
version: 1
date: '2021-02-11'
author: Michael Haag, Splunk
type: batch
datamodel: []
description: The following analytic identifies a renamed instance of hh.exe (HTML
  Help) executing a Compiled HTML Help (CHM). This particular technique will load
  Windows script code from a compiled help file. CHM files may contain nearly any
  file type embedded, but only execute html/htm. Upon a successful execution, the
  following script engines may be used for execution - JScript, VBScript, VBScript.Encode,
  JScript.Encode, JScript.Compact. Analyst may identify vbscript.dll or jscript.dll
  loading into hh.exe upon execution. The "htm" and "html" file extensions were the
  only extensions observed to be supported for the execution of Shortcut commands
  or WSH script code. During investigation, identify script content origination. Validate
  it is the legitimate version of hh.exe by reviewing the PE metadata. hh.exe is natively
  found in C:\Windows\system32 and C:\Windows\syswow64.
search: '`sysmon` EventID=1 OriginalFileName=HH.exe NOT process_name=hh.exe | stats
  count min(_time) as firstTime max(_time) as lastTime by Computer, User, parent_process_name,
  process_name, OriginalFileName, process_path, CommandLine | rename Computer as dest
  | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `detect_html_help_renamed_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting
  logs with the process name, parent process, and command-line executions from your
  endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the
  Sysmon TA. Tune and filter known instances where renamed hh.exe may be used.
known_false_positives: Although unlikely a renamed instance of hh.exe will be used
  legitimately, filter as needed.
references:
- https://attack.mitre.org/techniques/T1218/001/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.001/T1218.001.md
- https://lolbas-project.github.io/lolbas/Binaries/Hh/
tags:
  analytic_story:
  - Suspicious Compiled HTML Activity
  asset_type: Endpoint
  automated_detection_testing: passed
  cis20:
  - CIS 8
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1218.001/atomic_red_team/windows-sysmon.log
  kill_chain_phases:
  - Actions on Objectives
  mitre_attack_id:
  - T1218.001
  nist:
  - PR.PT
  - DE.CM
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - EventID
  - OriginalFileName
  - process_name
  - Computer
  - User
  - parent_process_name
  - process_path
  - CommandLine
  security_domain: endpoint
