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Description

The following analytic identifies a new service WerFaultSvc being created with a binary path located in the windows winsxs path. Per the report, the Snake version primarily discussed in this advisory registers a service to maintain persistence on a system. Typically this service is named WerFaultSvc which we assess was used to blend in with the legitimate Windows service WerSvc. On boot, this service will execute Snakes WerFault.exe, which Snake developers chose to hide among the numerous valid Windows WerFault.exe files in the windows WinSxS directory. Executing WerFault.exe will start the process of decrypting Snakes components and loading them into memory.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2023-05-11
  • Author: Michael Haag, Splunk
  • ID: 64eb091f-8cab-4b41-9b09-8fb4942377df

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1547.006 Kernel Modules and Extensions Persistence, Privilege Escalation
T1569.002 Service Execution Execution
Kill Chain Phase
  • Installation
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`wineventlog_system` EventCode=7045  ImagePath="*\\windows\\winSxS\\*" ImagePath="*\Werfault.exe" 
| stats count min(_time) as firstTime max(_time) as lastTime by Computer EventCode ImagePath ServiceName ServiceType 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_snake_malware_service_create_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_snake_malware_service_create_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • EventCode
  • Service_File_Name
  • Service_Type
  • _time
  • Service_Name
  • Service_Start_Type
  • Service_Account
  • user

How To Implement

To successfully implement this search, you need to be ingesting Windows System logs with the Service name, Service File Name Service Start type, and Service Type from your endpoints.

Known False Positives

False positives should be limited as this is a strict primary indicator used by Snake Malware.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
72.0 80 90 A service, WerFaultSvc, was created on $dest$ and is related to Snake Malware.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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

source | version: 1