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AWS Route 53 Private Hosted Zone Associated With a VPC

Identifies when an AWS Route 53 private hosted zone is associated with a new Virtual Private Cloud (VPC). Private hosted zones restrict DNS resolution to specific VPCs, and associating additional VPCs expands the scope of what networks can resolve internal DNS records. Adversaries with sufficient permissions may associate unauthorized VPCs to intercept, observe, or reroute internal traffic, establish persistence, or expand their visibility within an AWS environment.

Rule type: query
Rule indices:

  • filebeat-*
  • logs-aws.cloudtrail-*

Rule Severity: medium
Risk Score: 47
Runs every:
Searches indices from: now-6m
Maximum alerts per execution: ?
References:

Tags:

  • Domain: Cloud
  • Data Source: AWS
  • Data Source: Amazon Web Services
  • Data Source: AWS Route 53
  • Use Case: Asset Visibility
  • Tactic: Persistence
  • Tactic: Resource Development
  • Resources: Investigation Guide

Version: ?
Rule authors:

  • Austin Songer
  • Elastic

Rule license: Elastic License v2

Disclaimer: This investigation guide was created using generative AI technology and has been reviewed to improve its accuracy and relevance. While every effort has been made to ensure its quality, we recommend validating the content and adapting it to suit your specific environment and operational needs.

Route 53 private hosted zones provide internal DNS capabilities accessible only to the VPCs explicitly associated with them. Associating a new VPC expands DNS visibility and access. If an adversary gains sufficient IAM permissions, they may attach unauthorized VPCs to privileged hosted zones to perform internal reconnaissance, intercept service discovery, redirect traffic, or gain persistence by manipulating internal name resolution.

This rule detects successful AssociateVPCWithHostedZone events where a hosted zone's visibility scope is modified.

  • Identify the Actor

    • Review aws.cloudtrail.user_identity.arn and access_key_id to determine who initiated the association. Validate whether this identity is expected to manage Route 53 or VPC networking.

  • Review Request Details

    • Examine aws.cloudtrail.request_parameters to confirm which hosted zone and VPC were associated. Determine if the hosted zone contains sensitive internal service records, privileged DNS, or identity service endpoints.

  • Validate the VPC

    • Identify whether the associated VPC belongs to an authorized environment (e.g., known production, staging, or internal networks). Check for unusual VPC creation events, cross-account VPC behavior, or recently observed anomalous resource provisioning.

  • Assess Source Context

    • Inspect source.ip and user_agent.original for geographic anomalies, automation patterns, or suspicious tooling.
    • Look for correlations with unusual IAM activity, privilege escalations, or policy modifications.

  • Correlate With Broader Activity

    • Search for additional changes involving the same identity, including:
      • Route 53 hosted zone modifications
      • VPC peering creation
      • Network ACL or security group changes
      • IAM privilege modifications
    • Identify whether this association is part of a larger sequence suggesting lateral movement or internal reconnaissance.

  • Engage Relevant Teams

    • If initiated by a user, confirm intent with networking or cloud infrastructure teams. Validate whether the association aligns with deployment, migration, or environment expansion activities.

  • Routine Infrastructure Updates

    • Associations may occur during normal environment expansions (new VPC for microservices, deployments, region expansion).

  • Automated Tooling

    • Infrastructure-as-code pipelines (Terraform, CloudFormation, CDK) may regularly modify hosted zone associations.
    • If confirmed legitimate, consider excluding specific automation IAM roles.

  • Migration or Restructuring Events

    • Large-scale cloud migrations or VPC re-architecture work may trigger frequent legitimate associations.

  • Revoke Unauthorized Access

    • If the association is unauthorized, review and restrict IAM permissions for the actor.
    • Remove the VPC association if it is not intended.

  • Investigate Potential Impact

    • Review internal DNS query logs and VPC flow logs for any misuse, suspicious lookups, or unauthorized cross-VPC traffic.

  • Strengthen IAM Controls

    • Limit route53:AssociateVPCWithHostedZone to specific administrative roles.
    • Require MFA for accounts with Route 53 and VPC modification permissions.

  • Monitor for Related Activity

    • Add monitoring for other hosted zone modifications, new VPC creation, and cross-account network configurations.

  • Communicate and Document

    • Notify cloud networking and security operations of unauthorized changes.
    • Document findings and update policy controls or automation baselines.
event.dataset: aws.cloudtrail
    and event.provider: route53.amazonaws.com
    and event.action: AssociateVPCWithHostedZone
    and event.outcome: success

Framework: MITRE ATT&CK

Framework: MITRE ATT&CK