Detection: Windows Potential Cloudflared Network Connection

Description

This analytic detects network connection events possibly associated with the Cloudflared tool, a tool used to create tunnels via Cloudflare. Cloudflared is functionally very similar to ngrok, an ingress-as-a-service tool. It reaches out to the Cloudflare Edge Servers, creating an outbound connection over HTTPS(HTTP2/QUIC), where the tunnel's controller makes services or private networks accessible.

 1
 2| tstats `security_content_summariesonly`
 3   count min(_time) as firstTime
 4         max(_time) as lastTime
 5         values(All_Traffic.src_port) as src_port
 6
 7from datamodel=Network_Traffic.All_Traffic where
 8
 9All_Traffic.dest_port=7844
10
11BY All_Traffic.action All_Traffic.app All_Traffic.dest
12   All_Traffic.dest_ip All_Traffic.dest_port All_Traffic.direction
13   All_Traffic.dvc All_Traffic.protocol All_Traffic.protocol_version
14   All_Traffic.src All_Traffic.src_ip All_Traffic.transport
15   All_Traffic.user All_Traffic.vendor_product
16
17
18| `drop_dm_object_name(All_Traffic)`
19
20| `security_content_ctime(firstTime)`
21
22| `security_content_ctime(lastTime)`
23
24| `windows_potential_cloudflared_network_connection_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 3 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_potential_cloudflared_network_connection_filter search *
windows_potential_cloudflared_network_connection_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
T1572 Protocol Tunneling Command And Control
Command and Control
DE.AE
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 Risk Event False
This configuration file applies to all detections of type hunting.

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 use cases include authorized tunneling for remote access or service exposure in enterprise environments. Filter alerts for approved Cloudflared deployments to reduce false positives.

Associated Analytic Story

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