Create impact_gcp_service_account_disabled.toml (#320)

rules/gcp/impact_gcp_service_account_disabled.toml

@@ -0,0 +1,51 @@
+[metadata]
+creation_date = "2020/09/22"
+ecs_version = ["1.6.0"]
+maturity = "production"
+updated_date = "2020/09/22"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies when a service account is disabled in Google Cloud Platform (GCP). A service account is a special type of
+account used by an application or a virtual machine (VM) instance, not a person. Applications use service accounts to
+make authorized API calls, authorized as either the service account itself, or as G Suite or Cloud Identity users
+through domain-wide delegation. An adversary may disable a service account in order to disrupt to disrupt their target's
+business operations.
+"""
+false_positives = [
+    """
+    Service accounts may be disabled by system administrators. Verify that the behavior was expected. Exceptions can be
+    added to this rule to filter expected behavior.
+    """,
+]
+index = ["filebeat-*"]
+language = "kuery"
+license = "Elastic License"
+name = "GCP Service Account Disabled"
+note = "The GCP Filebeat module must be enabled to use this rule."
+references = ["https://cloud.google.com/iam/docs/service-accounts"]
+risk_score = 47
+rule_id = "bca7d28e-4a48-47b1-adb7-5074310e9a61"
+severity = "medium"
+tags = ["Elastic", "GCP", "Continuous Monitoring", "SecOps", "Identity and Access"]
+type = "query"
+
+query = '''
+event.module:googlecloud and event.dataset:googlecloud.audit and event.action:google.iam.admin.v*.DisableServiceAccount and event.outcome:success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1531"
+name = "Account Access Removal"
+reference = "https://attack.mitre.org/techniques/T1531/"
+
+
+[rule.threat.tactic]
+id = "TA0040"
+name = "Impact"
+reference = "https://attack.mitre.org/tactics/TA0040/"
+