[New Rule] GCP Firewall Rule Deleted (#310)

* new-rule-gcp-firewall-rule-deleted

* Update rule maturity to production

* Add FP info to rule

* Update rule maturity to production

* Add ATT&CK metadata

* Lint rule

* Update name to align with other rules

Co-authored-by: Brent Murphy <56412096+bm11100@users.noreply.github.com>

Co-authored-by: Brent Murphy <56412096+bm11100@users.noreply.github.com>

rules/gcp/defense_evasion_gcp_firewall_rule_deleted.toml

@@ -0,0 +1,48 @@
+[metadata]
+creation_date = "2020/09/21"
+ecs_version = ["1.6.0"]
+maturity = "production"
+updated_date = "2020/09/21"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies when a firewall rule is deleted in Google Cloud Platform (GCP). Virtual Private Cloud (VPC) firewall rules
+can be configured to allow or deny connections to or from virtual machine (VM) instances. An adversary may delete a
+firewall rule in order to weaken their target's security controls.
+"""
+false_positives = [
+    """
+    Firewall rules may be deleted by system administrators. Verify that the firewall configuration change was expected.
+    Exceptions can be added to this rule to filter expected behavior.
+    """,
+]
+index = ["filebeat-*"]
+language = "kuery"
+license = "Elastic License"
+name = "GCP Firewall Rule Deletion"
+note = "The GCP Filebeat module must be enabled to use this rule."
+references = ["https://cloud.google.com/vpc/docs/firewalls"]
+risk_score = 47
+rule_id = "ff9b571e-61d6-4f6c-9561-eb4cca3bafe1"
+severity = "medium"
+tags = ["Elastic", "GCP", "Continuous Monitoring", "SecOps", "Configuration Audit"]
+type = "query"
+
+query = '''
+event.module:googlecloud and event.dataset:googlecloud.audit and event.action:v*.compute.firewalls.delete
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1562"
+name = "Impair Defenses"
+reference = "https://attack.mitre.org/techniques/T1562/"
+
+
+[rule.threat.tactic]
+id = "TA0005"
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"