GCP Audit Logs - Open Firewall Rule Created or Modified

GCPAuditLogs
| where ServiceName == "compute.googleapis.com"
| where MethodName has_any ("firewalls.insert", "firewalls.patch")
| where GCPResourceType == "gce_firewall_rule"
| where Severity == "NOTICE"
| extend 
    RequestJson = parse_json(Request),
    RequestMetadataJson = parse_json(RequestMetadata),
    AuthInfoJson = parse_json(AuthenticationInfo)
| extend 
    SourceRanges = RequestJson.sourceRanges,
    Alloweds = RequestJson.alloweds,
    Direction = tostring(RequestJson.direction),
    RuleName = tostring(RequestJson.name),
    Network = tostring(RequestJson.network),
    Priority = tostring(RequestJson.priority),
    LogConfig = RequestJson.logConfig,
    Disabled = tobool(RequestJson.disabled)
| mv-expand SourceRange = SourceRanges
| extend SourceRangeStr = tostring(SourceRange)
| where SourceRangeStr in ("0.0.0.0/0", "0.0.0.0")
| extend 
    FirewallRuleName = extract(@"firewalls/([^/]+)$", 1, GCPResourceName),
    CallerIpAddress = tostring(RequestMetadataJson.callerIp),
    UserAgent = tostring(RequestMetadataJson.callerSuppliedUserAgent),
    AuthEmail = tostring(AuthInfoJson.principalEmail)
| mv-expand Allowed = Alloweds
| extend 
    AllowedProtocol = tostring(Allowed.IPProtocol),
    AllowedPorts = tostring(Allowed.ports),
    OperationType = case(
        MethodName has "insert", "Created",
        MethodName has "patch", "Modified",
        "Unknown")
| summarize 
    AllowedProtocols = make_set(AllowedProtocol, 30),
    AllowedPortsList = make_set(AllowedPorts, 100),
    SourceRangesList = make_set(SourceRangeStr, 100)
    by TimeGenerated, PrincipalEmail, AuthEmail, ProjectId, FirewallRuleName, 
       GCPResourceName, Direction, Priority, Network, CallerIpAddress, UserAgent, 
       MethodName, ServiceName, Severity, OperationType, LogName, InsertId
| extend
    AccountName = tostring(split(PrincipalEmail, "@")[0]), 
    AccountUPNSuffix = tostring(split(PrincipalEmail, "@")[1])
| project TimeGenerated,
          PrincipalEmail,
          AuthEmail,
          ProjectId,
          FirewallRuleName,
          ResourceName = GCPResourceName,
          OperationType,
          Direction,
          SourceRangesList,
          AllowedProtocols,
          AllowedPortsList,
          Priority,
          Network,
          CallerIpAddress,
          UserAgent,
          MethodName,
          ServiceName,
          Severity,
          LogName,
          InsertId,
          AccountName,
          AccountUPNSuffix

tags:
- GCP
- Firewall
- Network Security
- Misconfiguration
queryFrequency: 1h
kind: Scheduled
version: 1.0.0
relevantTechniques:
- T1562.004
- T1133
- T1562.001
alertDetailsOverride:
  alertDisplayNameFormat: GCP Open Firewall Rule {{OperationType}} - {{FirewallRuleName}} by {{PrincipalEmail}}
  alertDescriptionFormat: |-
    User {{PrincipalEmail}} created/modified firewall rule {{FirewallRuleName}} in project {{ProjectId}} to allow traffic from unrestricted sources (0.0.0.0/0).
    This configuration exposes resources to the internet and significantly increases attack surface. Investigate immediately to determine if this was authorized and assess potential security exposure. Consider restricting source ranges to specific trusted IP addresses or networks.    
triggerOperator: gt
customDetails:
  OperationType: OperationType
  FirewallRuleName: FirewallRuleName
  Direction: Direction
  ProjectId: ProjectId
  ResourceName: ResourceName
  AllowedProtocols: AllowedProtocols
  SourceRanges: SourceRangesList
  Network: Network
  AllowedPorts: AllowedPortsList
status: Available
requiredDataConnectors:
- connectorId: GCPAuditLogsDefinition
  dataTypes:
  - GCPAuditLogs
id: 8061c611-55f1-4ee5-a8f8-8f19f2c7aab2
name: GCP Audit Logs - Open Firewall Rule Created or Modified
query: |
  GCPAuditLogs
  | where ServiceName == "compute.googleapis.com"
  | where MethodName has_any ("firewalls.insert", "firewalls.patch")
  | where GCPResourceType == "gce_firewall_rule"
  | where Severity == "NOTICE"
  | extend 
      RequestJson = parse_json(Request),
      RequestMetadataJson = parse_json(RequestMetadata),
      AuthInfoJson = parse_json(AuthenticationInfo)
  | extend 
      SourceRanges = RequestJson.sourceRanges,
      Alloweds = RequestJson.alloweds,
      Direction = tostring(RequestJson.direction),
      RuleName = tostring(RequestJson.name),
      Network = tostring(RequestJson.network),
      Priority = tostring(RequestJson.priority),
      LogConfig = RequestJson.logConfig,
      Disabled = tobool(RequestJson.disabled)
  | mv-expand SourceRange = SourceRanges
  | extend SourceRangeStr = tostring(SourceRange)
  | where SourceRangeStr in ("0.0.0.0/0", "0.0.0.0")
  | extend 
      FirewallRuleName = extract(@"firewalls/([^/]+)$", 1, GCPResourceName),
      CallerIpAddress = tostring(RequestMetadataJson.callerIp),
      UserAgent = tostring(RequestMetadataJson.callerSuppliedUserAgent),
      AuthEmail = tostring(AuthInfoJson.principalEmail)
  | mv-expand Allowed = Alloweds
  | extend 
      AllowedProtocol = tostring(Allowed.IPProtocol),
      AllowedPorts = tostring(Allowed.ports),
      OperationType = case(
          MethodName has "insert", "Created",
          MethodName has "patch", "Modified",
          "Unknown")
  | summarize 
      AllowedProtocols = make_set(AllowedProtocol, 30),
      AllowedPortsList = make_set(AllowedPorts, 100),
      SourceRangesList = make_set(SourceRangeStr, 100)
      by TimeGenerated, PrincipalEmail, AuthEmail, ProjectId, FirewallRuleName, 
         GCPResourceName, Direction, Priority, Network, CallerIpAddress, UserAgent, 
         MethodName, ServiceName, Severity, OperationType, LogName, InsertId
  | extend
      AccountName = tostring(split(PrincipalEmail, "@")[0]), 
      AccountUPNSuffix = tostring(split(PrincipalEmail, "@")[1])
  | project TimeGenerated,
            PrincipalEmail,
            AuthEmail,
            ProjectId,
            FirewallRuleName,
            ResourceName = GCPResourceName,
            OperationType,
            Direction,
            SourceRangesList,
            AllowedProtocols,
            AllowedPortsList,
            Priority,
            Network,
            CallerIpAddress,
            UserAgent,
            MethodName,
            ServiceName,
            Severity,
            LogName,
            InsertId,
            AccountName,
            AccountUPNSuffix  
queryPeriod: 1h
triggerThreshold: 0
description: |
  'Detects when a Google Cloud Platform firewall rule is created or modified to allow traffic from any source (0.0.0.0/0 or 0.0.0.0).
  Open firewall rules expose resources to the internet and can significantly increase the attack surface of cloud infrastructure.
  This may indicate a misconfiguration, lack of security awareness, or malicious activity to create backdoor access.
  Adversaries may create or modify firewall rules to enable persistent access or facilitate lateral movement.
  This rule monitors firewall insert and patch operations where sourceRanges include unrestricted access patterns.'  
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: PrincipalEmail
  - identifier: Name
    columnName: AccountName
  - identifier: UPNSuffix
    columnName: AccountUPNSuffix
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: CallerIpAddress
- entityType: CloudApplication
  fieldMappings:
  - identifier: Name
    columnName: ProjectId
  - identifier: InstanceName
    columnName: ResourceName
severity: High
tactics:
- DefenseEvasion
- Persistence
- InitialAccess
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Google Cloud Platform Audit Logs/Analytic Rules/GCPOpenFirewallRuleCreated.yaml