[New Rule] GCP Service Account Created (#318)

* new-rule-gcp-service-account-created

* 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/persistence_gcp_service_account_created.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 new service account is created 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. If service accounts are not tracked and managed properly, they can present a security
+risk. An adversary may create a new service account to use during their operations in order to avoid using a standard
+user account and attempt to evade detection.
+"""
+false_positives = [
+    """
+    Service accounts can be created 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 Creation"
+note = "The GCP Filebeat module must be enabled to use this rule."
+references = ["https://cloud.google.com/iam/docs/service-accounts"]
+risk_score = 21
+rule_id = "7ceb2216-47dd-4e64-9433-cddc99727623"
+severity = "low"
+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*.CreateServiceAccount and event.outcome:success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1136"
+name = "Create Account"
+reference = "https://attack.mitre.org/techniques/T1136/"
+
+
+[rule.threat.tactic]
+id = "TA0003"
+name = "Persistence"
+reference = "https://attack.mitre.org/tactics/TA0003/"