[New Rule] Administrator Role Assigned to Okta User (#489)

* Create persistence_administrator_role_assigned_to_okta_user.toml

* set maturity to production

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

* Reorder references to put the most relevant at the top

* tweak rule name

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

rules/okta/persistence_administrator_role_assigned_to_okta_user.toml

@@ -0,0 +1,52 @@
+[metadata]
+creation_date = "2020/11/06"
+ecs_version = ["1.6.0"]
+maturity = "production"
+updated_date = "2020/11/06"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies when an administrator role is assigned to an Okta user. An adversary may attempt to assign an administrator
+role to an Okta user in order to assign additional permissions to a user account and maintain access to their target's
+environment.
+"""
+false_positives = [
+    """
+    Administrator roles may be assigned to Okta users by a Super Admin user. Verify that the behavior was expected.
+    Exceptions can be added to this rule to filter expected behavior.
+    """,
+]
+index = ["filebeat-*", "logs-okta*"]
+language = "kuery"
+license = "Elastic License"
+name = "Administrator Role Assigned to an Okta User"
+note = "The Okta Fleet integration or Filebeat module must be enabled to use this rule."
+references = [
+    "https://help.okta.com/en/prod/Content/Topics/Security/administrators-admin-comparison.htm",
+    "https://developer.okta.com/docs/reference/api/system-log/",
+    "https://developer.okta.com/docs/reference/api/event-types/",
+]
+risk_score = 47
+rule_id = "f06414a6-f2a4-466d-8eba-10f85e8abf71"
+severity = "medium"
+tags = ["Elastic", "Okta", "SecOps", "Monitoring", "Continuous Monitoring"]
+type = "query"
+
+query = '''
+event.dataset:okta.system and event.action:user.account.privilege.grant
+'''
+
+
+[[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 = "TA0003"
+name = "Persistence"
+reference = "https://attack.mitre.org/tactics/TA0003/"