GCP Logging Sink Modification

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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: 5 minutes

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Cloud
  • GCP
  • Continuous Monitoring
  • SecOps
  • Log Auditing

Version: 3 (version history)

Added (Elastic Stack release): 7.10.0

Last modified (Elastic Stack release): 7.11.2

Rule authors: Elastic

Rule license: Elastic License

Potential false positives

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Logging sink modifications may be done by a system or network administrator. Verify whether the user email, resource name, and/or hostname should be making changes in your environment. Sink modifications from unfamiliar users or hosts should be investigated. If known behavior is causing false positives, it can be exempted from the rule.

Investigation guide

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The GCP Filebeat module must be enabled to use this rule.

Rule query

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event.dataset:(googlecloud.audit or gcp.audit) and
event.action:google.logging.v*.ConfigServiceV*.UpdateSink and
event.outcome:success

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 3 (7.11.2 release)
  • Formatting only
Version 2 (7.11.0 release)
  • Updated query, changed from:

    event.dataset:googlecloud.audit and
    event.action:google.logging.v*.ConfigServiceV*.UpdateSink and
    event.outcome:success