TL;DR
Publishing your AWS Virtual Private Cloud (VPC) and Subnet IDs isn’t directly a massive security risk, but it can significantly increase the attack surface for targeted attacks. Attackers can use this information to map your infrastructure, identify potential vulnerabilities, and craft more effective phishing or exploitation attempts. It’s best practice to keep these IDs confidential where possible.
Understanding the Risks
VPC and Subnet IDs are like addresses for your cloud resources. While they don’t grant access themselves, knowing them helps attackers understand:
- Your Network Topology: They reveal how your network is structured within AWS.
- Resource Relationships: Attackers can identify which services and instances are connected to specific VPCs/Subnets.
- Potential Entry Points: Publicly accessible resources (like Load Balancers or NAT Gateways) associated with those IDs become more visible targets.
This information is particularly dangerous if combined with other publicly available data about your organisation.
Steps to Mitigate Risks
- Avoid Public Disclosure: This is the most important step.
- Don’t hardcode VPC/Subnet IDs in public code repositories (GitHub, GitLab etc.).
- Be careful when sharing configuration files or documentation publicly.
- Review any third-party tools or services you use to ensure they aren’t inadvertently exposing this information.
- Regularly Audit Public Sources: Check for accidental exposure.
- Use search engines (Google, DuckDuckGo) with specific ID strings to see if they appear in unexpected places. For example:
"vpc-xxxxxxxxxxxxxxxxx" site:.github.com - Utilise security scanning tools that can identify exposed AWS metadata.
- Use search engines (Google, DuckDuckGo) with specific ID strings to see if they appear in unexpected places. For example:
- Implement Strong Access Controls: Limit who can access and modify your VPC configuration.
- Use IAM roles with the principle of least privilege. Grant only necessary permissions to users and services.
- Enable Multi-Factor Authentication (MFA) for all AWS accounts.
- Network Segmentation: Reduce the blast radius of potential attacks.
- Divide your VPC into multiple subnets with different security requirements.
- Use Network Access Control Lists (NACLs) and Security Groups to control traffic flow between subnets.
- Monitor for Suspicious Activity: Detect potential attacks early.
- Enable AWS CloudTrail logging to track API calls made to your AWS account.
- Use Amazon GuardDuty or other intrusion detection systems to identify malicious activity within your VPCs.
- Consider Using PrivateLink: For services that need to communicate with each other, use AWS PrivateLink instead of public endpoints.
PrivateLink allows you to establish private connections between your VPCs and AWS services or other VPCs without exposing traffic to the internet.
Tools for Checking Exposure
- AWS Config: Can be used to audit resource configurations and identify potential security misconfigurations.
- Third-party Cloud Security Posture Management (CSPM) tools: Many CSPM tools offer features for identifying exposed AWS metadata, including VPC/Subnet IDs.