GCP Firewall Rule Modification

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: 5m

Searches indices from: None (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: 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:(*.compute.firewalls.patch or google.appengine.*.Firewall.Update*Rule)

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Impair Defenses
- ID: T1562
- Reference URL: https://attack.mitre.org/techniques/T1562/

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