GCP Logging Sink Modification

Identifies a modification to a logging sink in Google Cloud Platform (GCP). Logging compares the log entry to the sinks in that resource. Each sink whose filter matches the log entry writes a copy of the log entry to the sink’s export destination. An adversary may update a logging sink to exfiltrate logs to a different export destination.

Rule type: query

Rule indices:

filebeat-*
logs-gcp*

Severity: low

Risk score: 21

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/logging/docs/export#how_sinks_work

Tags:

Elastic
Cloud
GCP
Continuous Monitoring
SecOps
Log Auditing

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:google.logging.v*.ConfigServiceV*.UpdateSink and event.outcome:success

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Exfiltration
- ID: TA0010
- Reference URL: https://attack.mitre.org/tactics/TA0010/
Technique:
- Name: Transfer Data to Cloud Account
- ID: T1537
- Reference URL: https://attack.mitre.org/techniques/T1537/

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