[New Rule] AWS RDS Security Group Created (#1260)

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

rules/aws/persistence_rds_group_creation.toml

@@ -0,0 +1,55 @@
+[metadata]
+creation_date = "2021/06/05"
+maturity = "production"
+updated_date = "2021/06/05"
+
+[rule]
+author = ["Elastic", "Austin Songer"]
+description = "Identifies the creation of an Amazon Relational Database Service (RDS) Security Group."
+false_positives = [
+    """
+    A RDS security group 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. Security group 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 Security Group 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_CreateDBSecurityGroup.html"]
+risk_score = 21
+rule_id = "378f9024-8a0c-46a5-aa08-ce147ac73a4e"
+severity = "low"
+tags = ["Elastic", "Cloud", "AWS", "Continuous Monitoring", "SecOps", "Monitoring"]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.dataset:aws.cloudtrail and event.provider:rds.amazonaws.com and event.action:CreateDBSecurityGroup 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.technique.subtechnique]]
+id = "T1136.003"
+name = "Cloud Account"
+reference = "https://attack.mitre.org/techniques/T1136/003/"
+
+
+
+[rule.threat.tactic]
+id = "TA0003"
+name = "Persistence"
+reference = "https://attack.mitre.org/tactics/TA0003/"
+