Detection: GCP Kubernetes cluster pod scan detection

EXPERIMENTAL DETECTION

This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2024-05-18 ID: 19b53215-4a16-405b-8087-9e6acf619842 Author: Rod Soto, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic identifies unauthenticated requests to Kubernetes cluster pods. It detects this activity by analyzing GCP Pub/Sub messages for audit logs where the response status code is 401, indicating unauthorized access attempts. This activity is significant for a SOC because it may indicate reconnaissance or scanning attempts by an attacker trying to identify vulnerable pods. If confirmed malicious, this activity could lead to unauthorized access, allowing the attacker to exploit vulnerabilities within the cluster, potentially compromising sensitive data or gaining control over the Kubernetes environment.

Search

1`google_gcp_pubsub_message` category=kube-audit 
2|spath input=properties.log 
3|search responseStatus.code=401 
4|table sourceIPs{} userAgent verb requestURI responseStatus.reason properties.pod 
5| `gcp_kubernetes_cluster_pod_scan_detection_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
N/A	N/A	N/A	N/A	N/A

Macros Used

Name	Value
google_gcp_pubsub_message	`sourcetype="google:gcp:pubsub:message"`
gcp_kubernetes_cluster_pod_scan_detection_filter	`search *`

gcp_kubernetes_cluster_pod_scan_detection_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
T1526	Cloud Service Discovery	Discovery

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.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

You must install the GCP App for Splunk (version 2.0.0 or later), then configure stackdriver and set a Pub/Sub subscription to be imported to Splunk.

Known False Positives

Not all unauthenticated requests are malicious, but frequency, User Agent, source IPs and pods will provide context.

Associated Analytic Story

Kubernetes Scanning Activity

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
tbd	25	50	50

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	❌ Failing	N/A	`N/A`	`N/A`
Integration	❌ Failing	N/A	`N/A`	`N/A`

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: 2