Detect Windows Allow Firewall Rule Addition/Modification

id: 056593d4-ca3b-47a7-be9d-d1d0884a1d36
name: Detect Windows Allow Firewall Rule Addition/Modification
description: |
  This analytic rule detects any registry value creation or modification of Windows firewall registry keys to allow network traffic. This could be an indication of defense evasion by an adversary to allow network traffic to/from a compromised host.
severity: Medium
status: Available 
tags:
  - Schema: _ASim_RegistryEvent
    SchemaVersion: 0.1.2
requiredDataConnectors:
  - connectorId: CrowdStrikeFalconEndpointProtection
    dataTypes: 
      - CommonSecurityLog
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - SecurityAlert
  - connectorId: SentinelOne
    dataTypes:
      - SentinelOne_CL
  - connectorId: VMwareCarbonBlack
    dataTypes:
      - CarbonBlackEvents_CL
  - connectorId: CiscoSecureEndpoint
    dataTypes:
      - CiscoSecureEndpoint_CL
  - connectorId: TrendMicroApexOne
    dataTypes:
      - TMApexOneEvent
  - connectorId: TrendMicroApexOneAma
    dataTypes:
      - TMApexOneEvent
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - DefenseEvasion
relevantTechniques:
  - T1562
query: |
  // List of Windows Firewall registry keys to monitor
  let firewallRegistryList = dynamic([
        'HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Services\\SharedAccess\\Parameters\\FirewallPolicy\\RestrictedServices\\Static\\System',
        'HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Services\\SharedAccess\\Parameters\\FirewallPolicy\\RestrictedServices\\Configurable\\System',
        'HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Services\\SharedAccess\\Defaults\\FirewallPolicy\\FirewallRules',
        'HKEY_LOCAL_MACHINE\\SOFTWARE\\Policies\\Microsoft\\WindowsFirewall'
    ]);
  _ASim_RegistryEvent
  | where EventType in ('RegistryValueSet', 'RegistryKeyCreated') 
  | where RegistryKey has_any (firewallRegistryList) and RegistryValueData has_all ('Action=Allow', 'Active=TRUE')
  | project
      TimeGenerated,
      DvcHostname,
      ActorUsername,
      ActorUsernameType,
      ActingProcessId,
      ActingProcessName,
      ActingProcessCommandLine,
      RegistryKey,
      RegistryValue,
      RegistryValueType,
      RegistryValueData
  | extend HostName = tostring(split(DvcHostname, '.')[0])
  | extend DnsDomain = tostring(strcat_array(array_slice(split(DvcHostname, '.'), 1, -1), '.'))
  | extend Username = iff(tostring(ActorUsernameType) == 'Windows', tostring(split(ActorUsername, '\\')[1]), ActorUsername)
  | extend NTDomain = iff(tostring(ActorUsernameType) == 'Windows', tostring(split(ActorUsername, '\\')[0]), ActorUsername)
  | extend Username = iff(tostring(ActorUsernameType) == 'UPN', tostring(split(ActorUsername, '@')[0]), Username)
  | extend UPNSuffix = iff(tostring(ActorUsernameType) == 'UPN', tostring(split(ActorUsername, '@')[1]), '')
  | extend RegHive = tostring(split(RegistryKey, '\\')[0]), RegKey = tostring(strcat_array(array_slice(split(RegistryKey, '\\'), 1, -1), '\\')) 
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: DnsDomain
      - identifier: NTDomain
        columnName: NTDomain
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: Username
      - identifier: UPNSuffix
        columnName: UPNSuffix
      - identifier: NTDomain
        columnName: NTDomain
  - entityType: Process
    fieldMappings:
      - identifier: ProcessId
        columnName: ActingProcessId
      - identifier: CommandLine
        columnName: ActingProcessCommandLine
  - entityType: RegistryKey
    fieldMappings:
      - identifier: Hive
        columnName: RegHive
      - identifier: Key
        columnName: RegKey
  - entityType: RegistryValue
    fieldMappings:
      - identifier: Name
        columnName: RegistryValue
      - identifier: Value
        columnName: RegistryValueData
      - identifier: ValueType
        columnName: RegistryValueType
eventGroupingSettings:
  aggregationKind: singleAlert
alertDetailsOverride:
  alertDisplayNameFormat: "Allow Firewall Rule {{RegistryValueData}} added at registry key {{RegKey}} on {{HostName}}"
  alertDescriptionFormat: "An allow Firewall Rule {{RegistryValueData}} added at registry key {{RegKey}} by {{Username}}."
version: 1.0.0
kind: Scheduled