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splunk-security_content/detections/endpoint/detect_html_help_renamed.yml
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YAML

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