Securing inter-VPC traffic within an account or across multiple accounts (for example, security groups, network ACLs, VPC endpoint policies)

What is the difference between Security Groups and Network ACLs in AWS VPC?

Security Groups are stateful, operate at the instance level, and allow you to specify allowable traffic for instances. Network ACLs are stateless, operate at the subnet level, and allow you to specify allowable traffic for subnets.

Can you explain how Security Groups work when you need to secure traffic between instances in different VPCs?

Security Groups allow you to define rules that permit traffic from sources by IP ranges or other Security Groups. When securing traffic between instances in different VPCs, you can reference the Security Group of the instance in the peered VPC as a source (or destination) in your rules.

How do Network ACLs help in securing inter-VPC traffic when using VPC peering?

Network ACLs can be used to define allow or deny rules for traffic moving to and from subnets in a VPC. When VPCs are peered, Network ACLs can enforce rules on incoming and outgoing traffic to the peered VPC ensuring added security at the subnet level.

If using a VPC Endpoint, how does the policy attached to the endpoint enhance security for inter-VPC traffic?

VPC Endpoint policies allow you to control the use of the endpoint within a VPC. You can define which principals can access the services through the endpoint, and which actions they can perform, thus securing access to AWS services without requiring traffic to traverse the public internet.

Can you describe how AWS Resource Access Manager (RAM) can be used to share resources and secure inter-VPC traffic across multiple AWS accounts?

AWS RAM allows you to share AWS resources like Subnets, Transitive Peering Connections, and Routes across AWS accounts within the same organization, under service control policies. It secures inter-VPC traffic by ensuring only authorized accounts can access shared resources and enforces consistent security policies across accounts.

When using VPC Peering, how does the routing configuration affect the security of inter-VPC traffic?

In VPC Peering, route tables must be configured to include routes that point to the peer VPC. This affects security because traffic is allowed only if routes are properly set up to direct traffic between the peered VPCs, ensuring that no unintended traffic is allowed.

What role does the “VPC Flow Logs” feature play in monitoring and securing inter-VPC traffic?

VPC Flow Logs capture information about the IP traffic going to and from network interfaces in your VPC. They can be used to detect anomalous traffic patterns, monitor compliance with network policies, and aid in the auditing of traffic for security purposes.

How would you structure Security Group rules to ensure secure communication between an application server in one VPC and a database server in a different VPC?

I would structure Security Group rules to limit traffic to the specific IP addresses or Security Group of the database server and restrict the allowed traffic types to just the database port (e.g., TCP port 3306 for MySQL) to ensure that only the application server can communicate with the database server.

What precautions would you take when automating VPC security configuration across multiple accounts to ensure consistency in security postures?

When automating VPC security configurations, I would use Infrastructure as Code (IaC) tools like AWS CloudFormation or Terraform to ensure consistent deployment of security group rules and NACLs. I would also implement version control, peer reviews, and automated compliance checks using AWS Config or third-party tools to maintain security standards.

How can you prevent traffic from bypassing your VPC’s internet gateway and ensure secure, direct connections to AWS services?

You can prevent traffic from bypassing your VPC’s internet gateway by using VPC Endpoints, which provide secure, private connections to AWS services without the need for an internet gateway, NAT device, or VPN connection.

When securing VPC traffic, why is it important to consider the principle of least privilege, and how does it apply to Security Group and Network ACL configurations?

The principle of least privilege is important to ensure that only the necessary access is granted to reduce the attack surface. In the context of Security Group and Network ACL configurations, it means configuring rules to allow only the minimum required network traffic for an instance or subnet to operate as intended while blocking all other traffic.

In a scenario where multiple VPCs are connected through Transit Gateway, what security measures can be implemented to control inter-VPC traffic?

When using Transit Gateway, you can create route table associations and propagations to control inter-VPC traffic. Additionally, implementing security domains with Routing Tables to segment networks or apply Security Group and Network ACL rules to individual VPC connections can enhance the security of inter-VPC communications.