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Description

The following analytic identifies winhlp32.exe, found natively in c:\windows\, spawning a child process that loads a file out of appdata, programdata, or temp. Winhlp32.exe has a rocky past in that multiple vulnerabilities were found and added to MetaSploit. WinHlp32.exe is required to display 32-bit Help files that have the ".hlp" file name extension. This particular instance is related to a Remcos sample where dynwrapx.dll is added to the registry under inprocserver32, and later module loaded by winhlp32.exe to spawn wscript.exe and load a vbs or file from disk. During triage, review parallel processes to identify further suspicious behavior. Review module loads for unsuspecting unsigned modules. Capture any file modifications and analyze.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-10-05
  • Author: Michael Haag, Splunk
  • ID: d17dae9e-2618-11ec-b9f5-acde48001122

ATT&CK

ID Technique Tactic
T1055 Process Injection Defense Evasion, Privilege Escalation

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name=winhlp32.exe Processes.process IN ("*\\appdata\\*","*\\programdata\\*", "*\\temp\\*") by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.original_file_name Processes.process Processes.process_id Processes.parent_process_id 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `winhlp32_spawning_a_process_filter`

Associated Analytic Story

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Required field

  • _time
  • Processes.dest
  • Processes.user
  • Processes.parent_process_name
  • Processes.parent_process
  • Processes.original_file_name
  • Processes.process_name
  • Processes.process
  • Processes.process_id
  • Processes.parent_process_path
  • Processes.process_path
  • Processes.parent_process_id

Kill Chain Phase

  • Exploitation

Known False Positives

False positives should be limited as winhlp32.exe is typically not used with the latest flavors of Windows OS. However, filter as needed.

RBA

Risk Score Impact Confidence Message
80.0 80 100 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$, and is not typical activity for this process.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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