[New Rule] Microsoft 365 Exchange DLP Policy Removed (#600)

* [New Rule] O365 Exchange DLP Policy Removed

* rebrand to m365

* update description

rules/microsoft-365/defense_evasion_microsoft_365_exchange_dlp_policy_removed.toml

@@ -0,0 +1,51 @@
+[metadata]
+creation_date = "2020/11/20"
+maturity = "production"
+updated_date = "2020/11/20"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies when a Data Loss Prevention (DLP) policy is removed in Microsoft 365. An adversary may remove a DLP policy to
+evade existing DLP monitoring.
+"""
+false_positives = [
+    """
+    A DLP policy may be removed 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-*"]
+language = "kuery"
+license = "Elastic License"
+name = "Microsoft 365 Exchange DLP Policy Removed"
+note = "The Microsoft 365 Fleet integration or Filebeat module must be enabled to use this rule."
+references = [
+    "https://docs.microsoft.com/en-us/powershell/module/exchange/remove-dlppolicy?view=exchange-ps",
+    "https://docs.microsoft.com/en-us/microsoft-365/compliance/data-loss-prevention-policies?view=o365-worldwide",
+]
+risk_score = 47
+rule_id = "60f3adec-1df9-4104-9c75-b97d9f078b25"
+severity = "medium"
+tags = ["Elastic", "Cloud", "Microsoft 365", "Continuous Monitoring", "SecOps", "Configuration Audit"]
+type = "query"
+
+query = '''
+event.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:"Remove-DlpPolicy" and event.outcome:success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1562"
+name = "Impair Defenses"
+reference = "https://attack.mitre.org/techniques/T1562/"
+
+
+[rule.threat.tactic]
+id = "TA0005"
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"
+