GCP Storage Bucket Permissions Modification

Identifies when the Identity and Access Management (IAM) permissions are modified for a Google Cloud Platform (GCP) storage bucket. An adversary may modify the permissions on a storage bucket to weaken their target’s security controls or an administrator may inadvertently modify the permissions, which could lead to data exposure or loss.

Rule type: query

Rule indices:

filebeat-*
logs-gcp*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: None (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://cloud.google.com/storage/docs/access-control/iam-permissions

Tags:

Elastic
Cloud
GCP
Continuous Monitoring
SecOps
Identity and Access

Version: 8

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Setup

The GCP Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.

Rule query

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event.dataset:gcp.audit and event.action:"storage.setIamPermissions" and event.outcome:success

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: File and Directory Permissions Modification
- ID: T1222
- Reference URL: https://attack.mitre.org/techniques/T1222/

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