GCP Firewall Rule Modification

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Identifies when a firewall rule is modified in Google Cloud Platform (GCP) for Virtual Private Cloud (VPC) or App Engine. These firewall rules can be modified to allow or deny connections to or from virtual machine (VM) instances or specific applications. An adversary may modify an existing firewall rule in order to weaken their target’s security controls and allow more permissive ingress or egress traffic flows for their benefit.

Rule type: query

Rule indices:

  • filebeat-*
  • logs-gcp*

Severity: medium

Risk score: 47

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
  • Configuration Audit

Version: 102 (version history)

Added (Elastic Stack release): 7.10.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Firewall rules may be modified by system administrators. Verify that the firewall configuration change was expected. Exceptions can be added to this rule to filter expected behavior.

Investigation guide

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Rule query

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event.dataset:gcp.audit and event.action:(*.compute.firewalls.patch or
google.appengine.*.Firewall.Update*Rule)

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 102 (8.6.0 release)
  • Formatting only
Version 100 (8.5.0 release)
  • Formatting only
Version 7 (8.4.0 release)
  • Updated query, changed from:

    event.dataset:(googlecloud.audit or gcp.audit) and
    event.action:v*.compute.firewalls.patch
Version 5 (7.13.0 release)
  • Formatting only
Version 4 (7.12.0 release)
  • Formatting only
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:v*.compute.firewalls.patch