Detection rules › Splunk
Potential ngrok Tunnel - Windows (Windows Event Log)
ngrok is a reverse proxy utility with the ability to establish tunnels on targets using reverse SSH, even if the target does not have ngrok installed. Attackers have been observed abusing ngrok to establish persistence and perform lateral movement on compromised targets by exposing RDP services. This use case detects artifacts specific to RDP sessions established using ngrok
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Command & Control | T1572 Protocol Tunneling |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Security-Auditing | Event ID 4779 | A session was disconnected from a Window Station. |
Rule body yaml
id: '20681.36836'
title: Potential ngrok Tunnel - Windows
description: 'ngrok is a reverse proxy utility with the ability to establish tunnels
on targets using reverse SSH, even if the target does not have ngrok installed.
Attackers have been observed abusing ngrok to establish persistence and perform
lateral movement on compromised targets by exposing RDP services. This use case
detects artifacts specific to RDP sessions established using ngrok. -- Threat Actor
Association: Scattered Spider (aka. Muddled Libra, Scatter Swine, Starfraud, UNC3944)'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4779) OR
"<EventID>4779<") "%16777216" | table _time, host, user, process_*, src_ip, src_port,
dest_ip, dest_port | bin span=1s | stats values(*) as * by _time, host '
techniques:
- command-and-control:protocol tunneling
technique_id:
- T1572
data_category:
- Windows event logs
references:
- https://www.logpoint.com/en/blog/a-deep-look-at-the-darkside-ransomware-operators-and-their-affiliates/
- https://ngrok.com/docs/secure-tunnels/tunnels/ssh-reverse-tunnel-agent/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4779) OR "<EventID>4779<") "%16777216"
Stage 2: table
| table _time, host, user, process_*, src_ip, src_port, dest_ip, dest_port
Stage 3: bucket
| bin span=1s
Stage 4: stats
| stats values(*) as * by _time, host
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
EventCode | eq |
|
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | TERM |
| 1 | "<EventID>4779<" |
| 1 | "%16777216" |