Create collection_microsoft_365_new_inbox_rule.toml (#1068)

Co-authored-by: Justin Ibarra <brokensound77@users.noreply.github.com>
Co-authored-by: David French <56409778+threat-punter@users.noreply.github.com>

rules/microsoft-365/collection_microsoft_365_new_inbox_rule.toml

@@ -0,0 +1,60 @@
+[metadata]
+creation_date = "2021/03/29"
+maturity = "production"
+updated_date = "2021/03/29"
+
+[rule]
+author = ["Elastic", "Gary Blackwell", "Austin Songer"]
+description = """
+Identifies when a new Inbox rule is created in Microsoft 365. Inbox rules process messages in the Inbox based on
+conditions and take actions, such as moving a message to a specified folder or deleting a message. Adequate permissions
+are required on the mailbox to create an Inbox rule.
+"""
+false_positives = [
+    """
+    An inbox rule may be created by a system or network administrator. Verify that the configuration change was
+    expected. Exceptions can be added to this rule to filter expected behavior.
+    """,
+]
+from = "now-30m"
+index = ["filebeat-*", "logs-o365*"]
+language = "kuery"
+license = "Elastic License v2"
+name = "Microsoft 365 New Inbox Rule Created"
+note = "The Microsoft 365 Fleet integration or Filebeat module must be enabled to use this rule."
+references = [
+    "https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/responding-to-a-compromised-email-account?view=o365-worldwide",
+    "https://docs.microsoft.com/en-us/powershell/module/exchange/new-inboxrule?view=exchange-ps",
+    "https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/detect-and-remediate-outlook-rules-forms-attack?view=o365-worldwide",
+]
+risk_score = 21
+rule_id = "ec8efb0c-604d-42fa-ac46-ed1cfbc38f78"
+severity = "low"
+tags = ["Elastic", "Cloud", "Microsoft 365", "Continuous Monitoring", "SecOps", "Configuration Audit"]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:"New-InboxRule" and event.outcome:success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+name = "Email Collection"
+reference = "https://attack.mitre.org/techniques/T1114/"
+id = "T1114"
+
+[[rule.threat.technique.subtechnique]]
+name = "Email Forwarding Rule"
+reference = "https://attack.mitre.org/techniques/T1114/003/"
+id = "T1114.003"
+
+
+
+[rule.threat.tactic]
+name = "Collection"
+reference = "https://attack.mitre.org/tactics/TA0009/"
+id = "TA0009"
+