Detection: Windows WinLogon with Public Network Connection

Description

The following analytic detects instances of Winlogon.exe, a critical Windows process, connecting to public IP addresses. This behavior is identified using Endpoint Detection and Response (EDR) telemetry, focusing on network connections made by Winlogon.exe. Under normal circumstances, Winlogon.exe should not connect to public IPs, and such activity may indicate a compromise, such as the BlackLotus bootkit attack. This detection is significant as it highlights potential system integrity breaches. If confirmed malicious, attackers could maintain persistence, bypass security measures, and compromise the system at a fundamental level.

Search

 1
 2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name IN (winlogon.exe)  Processes.process!=unknown by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id 
 3| `drop_dm_object_name(Processes)` 
 4| `security_content_ctime(firstTime)` 
 5| `security_content_ctime(lastTime)` 
 6| join  process_id [
 7| tstats `security_content_summariesonly` count FROM datamodel=Network_Traffic.All_Traffic where All_Traffic.dest_port != 0 NOT (All_Traffic.dest IN (127.0.0.1,10.0.0.0/8,172.16.0.0/12, 192.168.0.0/16, 0:0:0:0:0:0:0:1)) by All_Traffic.process_id All_Traffic.dest All_Traffic.dest_port 
 8| `drop_dm_object_name(All_Traffic)` 
 9| rename dest as publicIp ] 
10| table dest parent_process_name process_name process_path process process_id dest_port publicIp 
11| `windows_winlogon_with_public_network_connection_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 1	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Sysmon EventID 3	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Annotations

Default Configuration

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

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

False positives will be present and filtering will be required. Legitimate IPs will be present and need to be filtered.

Associated Analytic Story

• BlackLotus Campaign

Risk Based Analytics (RBA)

References

• https://www.microsoft.com/en-us/security/blog/2023/04/11/guidance-for-investigating-attacks-using-cve-2022-21894-the-blacklotus-campaign/

Detection Testing

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: 4