GitHub Repo

Detection: Windows SoftEther VPN Masquerading as Legitimate Binary

Updated Date: 2026-04-13 ID: 69fe4cb7-807e-4012-a17f-cd288215b038 Author: Raven Tait, Splunk Type: TTP Product: Splunk Enterprise Security

Description

Flax Typhoon actors have been identified downloading and using SoftEther VPN software to obfuscate their activity. This searches for the SoftEther VPN binary running with the obfuscated binary names they use for the process.

 1`sysmon`
 2EventID=1
 3process IN (
 4    "*conhost.exe*",
 5    "*dllhost.exe*"
 6)
 7AND
 8(
 9    Company="*SoftEther*"
10    OR
11    OriginalFileName="vpnbridge*.exe"
12)
13
14| fillnull
15
16| stats count min(_time) as firstTime
17              max(_time) as lastTime
18  by Computer EventID Company process action dest original_file_name
19     parent_process parent_process_exec parent_process_guid parent_process_id
20     parent_process_name parent_process_path process_hash process_integrity_level user
21     user_id vendor_product
22
23
24| `security_content_ctime(firstTime)`
25
26| `security_content_ctime(lastTime)`
27
28| `windows_softether_vpn_masquerading_as_legitimate_binary_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 1 Windows icon Windows 'XmlWinEventLog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_softether_vpn_masquerading_as_legitimate_binary_filter search *
windows_softether_vpn_masquerading_as_legitimate_binary_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1036 Masquerading Stealth
T1572 Protocol Tunneling Command And Control
Command and Control
Exploitation
DE.CM
CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

Some legitimate users may run SoftEther VPN for remote access or privacy purposes. Exclude known approved VPN usage to reduce false alerts.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Potential SoftEther VPN Masquerading as Legitimate Binary activity observed on $dest$.

Risk Object Risk Object Type Risk Score Threat Objects
dest system 50 No Threat Objects

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog

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: GitHub | Version: 1