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Description

This search looks for GCP PubSub events where a user has created an open/public GCP Storage bucket.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel:
  • Last Updated: 2020-08-05
  • Author: Shannon Davis, Splunk
  • ID: f6ea3466-d6bb-11ea-87d0-0242ac130003

ATT&CK

ID Technique Tactic
T1530 Data from Cloud Storage Object Collection
`google_gcp_pubsub_message` data.resource.type=gcs_bucket data.protoPayload.methodName=storage.setIamPermissions 
| spath output=action path=data.protoPayload.serviceData.policyDelta.bindingDeltas{}.action 
| spath output=user path=data.protoPayload.authenticationInfo.principalEmail 
| spath output=location path=data.protoPayload.resourceLocation.currentLocations{} 
| spath output=src path=data.protoPayload.requestMetadata.callerIp 
| spath output=bucketName path=data.protoPayload.resourceName 
| spath output=role path=data.protoPayload.serviceData.policyDelta.bindingDeltas{}.role 
| spath output=member path=data.protoPayload.serviceData.policyDelta.bindingDeltas{}.member 
| search (member=allUsers AND action=ADD) 
| table  _time, bucketName, src, user, location, action, role, member 
| search `detect_new_open_gcp_storage_buckets_filter`

Associated Analytic Story

How To Implement

This search relies on the Splunk Add-on for Google Cloud Platform, setting up a Cloud Pub/Sub input, along with the relevant GCP PubSub topics and logging sink to capture GCP Storage Bucket events (https://cloud.google.com/logging/docs/routing/overview).

Required field

  • _time
  • data.resource.type
  • data.protoPayload.methodName
  • data.protoPayload.serviceData.policyDelta.bindingDeltas{}.action
  • data.protoPayload.authenticationInfo.principalEmail
  • data.protoPayload.resourceLocation.currentLocations{}
  • data.protoPayload.requestMetadata.callerIp
  • data.protoPayload.resourceName
  • data.protoPayload.serviceData.policyDelta.bindingDeltas{}.role
  • data.protoPayload.serviceData.policyDelta.bindingDeltas{}.member

Kill Chain Phase

  • Actions on Objectives

Known False Positives

While this search has no known false positives, it is possible that a GCP admin has legitimately created a public bucket for a specific purpose. That said, GCP strongly advises against granting full control to the "allUsers" group.

Reference

Test Dataset

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

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