Detection: Ngrok Reverse Proxy on Network

Updated Date: 2024-09-30 ID: 5790a766-53b8-40d3-a696-3547b978fcf0 Author: Michael Haag, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects DNS queries to common Ngrok domains, indicating potential use of the Ngrok reverse proxy tool. It leverages the Network Resolution datamodel to identify queries to domains such as ".ngrok.com" and ".ngrok.io". While Ngrok usage is not inherently malicious, it has been increasingly adopted by adversaries for covert communication and data exfiltration. If confirmed malicious, this activity could allow attackers to bypass network defenses, establish persistent connections, and exfiltrate sensitive data, posing a significant threat to the network's security.

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime  from datamodel=Network_Resolution where DNS.query IN ("*.ngrok.com","*.ngrok.io", "ngrok.*.tunnel.com", "korgn.*.lennut.com") by DNS.src DNS.query DNS.answer 
3|  `drop_dm_object_name("DNS")` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `ngrok_reverse_proxy_on_network_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 22 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($field$)
ngrok_reverse_proxy_on_network_filter search *
ngrok_reverse_proxy_on_network_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
T1090 Proxy Command And Control
T1102 Web Service Command And Control
KillChainPhase.COMMAND_AND_CONTROL
NistCategory.DE_AE
Cis18Value.CIS_13
Chimera
Cinnamon Tempest
Cobalt Group
Ember Bear
FIN13
FIN6
Fox Kitten
Leviathan
Magic Hound
OilRig
APT41
Blue Mockingbird
Cinnamon Tempest
CopyKittens
Earth Lusca
Fox Kitten
LAPSUS$
Magic Hound
MoustachedBouncer
POLONIUM
Sandworm Team
Turla
Volt Typhoon
Windigo
APT32
EXOTIC LILY
FIN6
FIN8
Fox Kitten
Gamaredon Group
Inception
LazyScripter
Mustang Panda
RedCurl
Rocke
TeamTNT
Turla

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 True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

The Network Resolution Datamodel will need to have data mapped to it regarding DNS queries. Modify query as needed to use another source.

Known False Positives

False positives will be present based on organizations that allow the use of Ngrok. Filter or monitor as needed.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
An endpoint, $src$, is beaconing out to the reverse proxy service of Ngrok. 50 50 100
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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: 3