[New Rule] AWS RDS Security Group Deleted (#1261)

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

rules/aws/impact_rds_group_deletion.toml

@@ -0,0 +1,51 @@
+[metadata]
+creation_date = "2021/06/05"
+maturity = "production"
+updated_date = "2021/06/05"
+
+[rule]
+author = ["Elastic", "Austin Songer"]
+description = "Identifies the deletion of an Amazon Relational Database Service (RDS) Security Group."
+false_positives = [
+    """
+    A RDS security group deletion may be done 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 deletions 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 Deletion"
+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_DeleteDBSecurityGroup.html"]
+risk_score = 21
+rule_id = "863cdf31-7fd3-41cf-a185-681237ea277b"
+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:DeleteDBSecurityGroup and event.outcome:success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1531"
+name = "Account Access Removal"
+reference = "https://attack.mitre.org/techniques/T1531/"
+
+
+[rule.threat.tactic]
+id = "TA0040"
+name = "Impact"
+reference = "https://attack.mitre.org/tactics/TA0040/"
+