[New Rule] GCP IAM Service Account Key Deletion (#309)

* Create credential_access_gcp_iam_service_account_key_deletion.toml

* remove extra word in fp info

* linting

rules/gcp/credential_access_gcp_iam_service_account_key_deletion.toml

@@ -0,0 +1,54 @@
+[metadata]
+creation_date = "2020/09/21"
+ecs_version = ["1.6.0"]
+maturity = "production"
+updated_date = "2020/09/21"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies the deletion of an Identity and Access Management (IAM) service account key in Google Cloud Platform (GCP).
+Each service account is associated with two sets of public/private RSA key pairs that are used to authenticate. If a key
+is deleted, the application will no longer be able to access Google Cloud resources using that key. A security best
+practice is to rotate your service account keys regularly.
+"""
+false_positives = [
+    """
+    Service account key deletions may be done by a system or network administrator. Verify whether the user email,
+    resource name, and/or hostname should be making changes in your environment. Key deletions from unfamiliar users or
+    hosts should be investigated. If known behavior is causing false positives, it can be exempted from the rule.
+    """,
+]
+index = ["filebeat-*"]
+language = "kuery"
+license = "Elastic License"
+name = "GCP IAM Service Account Key Deletion"
+note = "The GCP Filebeat module must be enabled to use this rule."
+references = [
+    "https://cloud.google.com/iam/docs/service-accounts",
+    "https://cloud.google.com/iam/docs/creating-managing-service-account-keys",
+]
+risk_score = 21
+rule_id = "9890ee61-d061-403d-9bf6-64934c51f638"
+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*.DeleteServiceAccountKey and event.outcome:success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1098"
+name = "Account Manipulation"
+reference = "https://attack.mitre.org/techniques/T1098/"
+
+
+[rule.threat.tactic]
+id = "TA0006"
+name = "Credential Access"
+reference = "https://attack.mitre.org/tactics/TA0006/"
+