Detection: Windows TOR Client Execution

Description

The following analytic detects the execution of the TOR Browser and related TOR components on Windows endpoints by monitoring process creation activity. Adversaries and insider threats leverage TOR to anonymize command-and-control traffic, facilitate data exfiltration, and evade network monitoring and policy enforcement. While TOR can be used for legitimate research and privacy purposes, its presence on enterprise endpoints is often unusual and should be investigated to determine intent, scope, and any associated malicious behavior.

Search

 1
 2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
 3  from datamodel=Endpoint.Processes where
 4  (
 5    Processes.process_name = "tor.exe"
 6    OR
 7    (
 8      Processes.process_path = "*\\BraveSoftware\\Brave-Browser*"
 9      Processes.process_path = "*\\tor-*"
10    )
11  )
12  by Processes.action Processes.dest Processes.original_file_name
13     Processes.parent_process Processes.parent_process_exec
14     Processes.parent_process_guid Processes.parent_process_id
15     Processes.parent_process_name Processes.parent_process_path
16     Processes.process Processes.process_exec Processes.process_guid
17     Processes.process_hash Processes.process_id Processes.process_integrity_level
18     Processes.process_name Processes.process_path Processes.user
19     Processes.user_id Processes.vendor_product
20
21| `drop_dm_object_name(Processes)`
22
23| `security_content_ctime(firstTime)`
24
25| `security_content_ctime(lastTime)`
26
27| `windows_tor_client_execution_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	Other	'crowdstrike:events:sensor'	'crowdstrike'
Sysmon EventID 1	Windows	'XmlWinEventLog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688	Windows	'XmlWinEventLog'	'XmlWinEventLog:Security'

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

This detection focuses on TOR-related processes and may generate benign matches in environments where TOR is intentionally used, such as security testing, research, or lab environments.

Associated Analytic Story

• Command And Control

• Compromised Windows Host

• Data Exfiltration

• Data Protection

• Windows Post-Exploitation

Risk Based Analytics (RBA)

Risk Message:

TOR client process $process_name$ was launched by parent process $parent_process_name$ on host $dest$ by the user $user$ with command line $process$

References

• https://unit42.paloaltonetworks.com/tor-traffic-enterprise-networks/

• https://attack.mitre.org/software/S0183/

• https://attack.mitre.org/techniques/T1090/003/

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: 1