[New Rule] AWS RDS Instance Creation (#1269)

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

rules/aws/persistence_rds_instance_creation.toml

@@ -0,0 +1,45 @@
+[metadata]
+creation_date = "2021/06/06"
+maturity = "production"
+updated_date = "2021/06/06"
+
+[rule]
+author = ["Elastic"]
+description = "Identifies the creation of an Amazon Relational Database Service (RDS) Aurora database instance."
+false_positives = [
+    """
+    A database instance may be created by a system or network administrator. Verify whether the user identity, user
+    agent, and/or hostname should be making changes in your environment. Instances creations from unfamiliar users or
+    hosts should be investigated. If known behavior is causing false positives, it can be exempted from the rule.
+    """,
+]
+from = "now-60m"
+index = ["filebeat-*", "logs-aws*"]
+interval = "10m"
+language = "kuery"
+license = "Elastic License v2"
+name = "AWS RDS Instance Creation"
+note = """## Config
+
+The AWS Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule."""
+references = ["https://docs.aws.amazon.com/AmazonRDS/latest/APIReference/API_CreateDBInstance.html"]
+risk_score = 21
+rule_id = "f30f3443-4fbb-4c27-ab89-c3ad49d62315"
+severity = "low"
+tags = ["Elastic", "Cloud", "AWS", "Continuous Monitoring", "SecOps", "Asset Visibility"]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.dataset:aws.cloudtrail and event.provider:rds.amazonaws.com and event.action:CreateDBInstance and event.outcome:success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[rule.threat.tactic]
+id = "TA0003"
+name = "Persistence"
+reference = "https://attack.mitre.org/tactics/TA0003/"
+