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Azure Kubernetes Service scan fingerprinting

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A Kubernetes cluster is a set of worker machines, called nodes, that run containerized applications. A cluster usually runs multiple nodes to provide fault-tolerance and high availability. The cluster master runs the Kubernetes API server, scheduler, and core resource controllers. One of your concerns with using Kubernetes is fingerprinting. You want a search that shows unauthenticated requests via source IP address, user agent, request URI, and response status data against your Kubernetes cluster in Azure.

Required data

Procedure

  1. Ensure that you have configured Kube-Audit data diagnostics in the Splunk Add-on for Microsoft Cloud Services.
  2. Run the following search. You can optimize it by specifying an index and adjusting the time range.  
sourcetype:mscs:storage:blob:json category=kube-audit 
| spath input=properties.log 
| search responseStatus.code=401 
| table sourceIPs{} userAgent verb requestURI responseStatus.reason

Search explanation

The table provides an explanation of what each part of this search achieves. You can adjust this query based on the specifics of your environment.

Splunk Search Explanation

sourcetype:mscs:storage:blob:json

Search only the source type mscs:storage:blob:json.

category=kube-audit

Search the data source kube-audit from the diagnostic logs in Azure Cloud services.

| spath input=properties.log 

Pull information from this specific Kubernetes audit log.

| search responseStatus.code=401 

Search for HTTP Status 401, an unauthorized request.

| table sourceIPs{} userAgent verb requestURI responseStatus.reason 

Display the results in a table with columns in the order shown.

Next steps

Not all unauthenticated requests are malicious, but the strings provided in this search provide context. Analyze the following to determine what needs further investigation:

  • Source IP address reputation, geolocation, and access policy
  • Banners in the user agent for scanning tools, such as Zgrab or Nmap
  • Targeted files, directories or command strings in the request URI field 
  • A high number of forbidden, unauthorized, or failure responses

For additional information about this search, such as its applicability to common frameworks and standards, see this project on GitHub.

Finally, you might be interested in other processes associated with the Detecting Kubernetes scanning activity use case.