ID | Technique | Tactic |
---|---|---|
T1530 | Data from Cloud Storage | Collection |
Detection: Detect New Open GCP Storage Buckets
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.
Description
The following analytic identifies the creation of new open/public GCP Storage buckets. It leverages GCP PubSub events, specifically monitoring for the storage.setIamPermissions
method and checks if the allUsers
member is added. This activity is significant because open storage buckets can expose sensitive data to the public, posing a severe security risk. If confirmed malicious, an attacker could access, modify, or delete data within the bucket, leading to data breaches and potential compliance violations.
Search
1`google_gcp_pubsub_message` data.resource.type=gcs_bucket data.protoPayload.methodName=storage.setIamPermissions
2| spath output=action path=data.protoPayload.serviceData.policyDelta.bindingDeltas{}.action
3| spath output=user path=data.protoPayload.authenticationInfo.principalEmail
4| spath output=location path=data.protoPayload.resourceLocation.currentLocations{}
5| spath output=src path=data.protoPayload.requestMetadata.callerIp
6| spath output=bucketName path=data.protoPayload.resourceName
7| spath output=role path=data.protoPayload.serviceData.policyDelta.bindingDeltas{}.role
8| spath output=member path=data.protoPayload.serviceData.policyDelta.bindingDeltas{}.member
9| search (member=allUsers AND action=ADD)
10| table _time, bucketName, src, user, location, action, role, member
11| search `detect_new_open_gcp_storage_buckets_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" |
detect_new_open_gcp_storage_buckets_filter | search * |
detect_new_open_gcp_storage_buckets_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
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).
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.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
tbd | 25 | 50 | 50 |
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