splunk-security_content/docs/_posts/2021-04-19-wermgr_process_create_executable_file.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Wermgr Process Create Executable File	Obfuscated Files or Information	Endpoint	2021-04-19	true		Obfuscated Files or Information Defense Evasion Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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Description

this search is designed to detect potential malicious wermgr.exe process that drops or create executable file. Since wermgr.exe is an application trigger when error encountered in a process, it is really un ussual to this process to drop executable file. This technique is commonly seen in trickbot malware where it injects it code to this process to execute it malicious behavior like downloading other payload

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-04-19
• Author: Teoderick Contreras, Splunk
• ID: ab3bcce0-a105-11eb-973c-acde48001122

ATT&CK

ID	Technique	Tactic
T1027	Obfuscated Files or Information	Defense Evasion

Search

`sysmon` EventCode=11 process_name = "wermgr.exe" TargetFilename = "*.exe" 
| stats  min(_time) as firstTime max(_time) as lastTime count by  Image TargetFilename process_name dest EventCode ProcessId 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `wermgr_process_create_executable_file_filter`

Associated Analytic Story

• Trickbot

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 of wermgr.exe may be used.

Required field

• _time
• Image
• TargetFilename
• process_name
• dest
• EventCode
• ProcessId

Kill Chain Phase

• Exploitation

Known False Positives

unknown

RBA

Risk Score	Impact	Confidence	Message
56.0	70	80	Wermgr.exe writing executable files on dest

Reference

• https://labs.vipre.com/trickbot-and-its-modules/
• https://blog.whitehat.eu/2019/05/incident-trickbot-ryuk-2.html

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

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/trickbot/infection/windows-sysmon.log

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