[New Rule] Okta User Session Impersonation (#1867)

* [New Rule] Okta User Session Impersonation
Co-authored-by: Jonhnathan <jonhnathancesar@gmail.com>

(cherry picked from commit 46c2383e5b)

rules/integrations/okta/credential_access_user_impersonation_access.toml

@@ -0,0 +1,44 @@
+[metadata]
+creation_date = "2022/03/22"
+maturity = "production"
+updated_date = "2022/03/22"
+integration = "okta"
+
+[rule]
+author = ["Elastic"]
+description = """
+A user has initiated a session impersonation granting them access to the environment with the permissions of the user
+they are impersonating. This would likely indicate Okta administrative access and should only ever occur if requested
+and expected.
+"""
+from = "now-30m"
+index = ["filebeat-*", "logs-okta*"]
+interval = "15m"
+language = "kuery"
+license = "Elastic License v2"
+name = "Okta User Session Impersonation"
+note = """## Config
+
+The Okta Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule."""
+references = [
+    "https://blog.cloudflare.com/cloudflare-investigation-of-the-january-2022-okta-compromise/"
+]
+risk_score = 73
+rule_id = "cdbebdc1-dc97-43c6-a538-f26a20c0a911"
+severity = "high"
+tags = ["Elastic", "Identity", "Okta", "Continuous Monitoring", "SecOps", "Identity and Access", "Credential Access"]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.dataset:okta.system and event.action:user.session.impersonation.initiate
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[rule.threat.tactic]
+id = "TA0006"
+name = "Credential Access"
+reference = "https://attack.mitre.org/tactics/TA0006/"