[New Rule] Azure Firewall Policy Deletion (#169)

* Create defense_evasion_firewall_policy_deletion.toml

* Update rules/azure/defense_evasion_firewall_policy_deletion.toml

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

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

rules/azure/defense_evasion_firewall_policy_deletion.toml

@@ -0,0 +1,49 @@
+[metadata]
+creation_date = "2020/08/18"
+ecs_version = ["1.6.0"]
+maturity = "production"
+updated_date = "2020/08/18"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies the deletion of a firewall policy in Azure. An adversary may delete a firewall policy in an attempt to evade
+defenses and/or to eliminate barriers in carrying out their initiative.
+"""
+false_positives = [
+    """
+    Firewall policy deletions may be done by a system or network administrator. Verify whether the username, hostname,
+    and/or resource name should be making changes in your environment. Firewall policy 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-25m"
+index = ["filebeat-*"]
+language = "kuery"
+license = "Elastic License"
+name = "Azure Firewall Policy Deletion"
+note = "The Azure Filebeat module must be enabled to use this rule."
+references = ["https://docs.microsoft.com/en-us/azure/firewall-manager/policy-overview"]
+risk_score = 21
+rule_id = "e02bd3ea-72c6-4181-ac2b-0f83d17ad969"
+severity = "low"
+tags = ["Azure", "Elastic", "SecOps", "Continuous Monitoring", "Network"]
+type = "query"
+
+query = '''
+event.module:azure and event.dataset:azure.activitylogs and event.category:Administrative and azure.activitylogs.operation_name:MICROSOFT.NETWORK/FIREWALLPOLICIES/DELETE and event.outcome:Success
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1089"
+name = "Disabling Security Tools"
+reference = "https://attack.mitre.org/techniques/T1089/"
+
+
+[rule.threat.tactic]
+id = "TA0005"
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"