Cross transit connectivity is allowed by EC2

Security & Compliance

Cross transit connectivity in EC2 refers to the ability of an EC2 instance to communicate with another instance in a different subnet or VPC. This can be a security risk if the communication is not authorized or controlled. When cross transit connectivity is allowed by EC2, it means that the security group or network ACL associated with the instance allows traffic to flow freely between subnets or VPCs, regardless of whether it is authorized or not. This can create a risk of unauthorized access or data exfiltration if an attacker gains access to one of the instances and is able to exploit the cross transit connectivity to move laterally across the network. To ensure the security of your EC2 instances, it is important to restrict cross transit connectivity only to authorized traffic and implement appropriate network segmentation to limit access to resources.‍


To remediate the issue of cross transit connectivity being allowed by EC2, the following steps can be taken:

  1. Review the existing security group and network ACL settings to identify any rules that allow traffic to flow freely between subnets or VPCs.
  2. Update the security group and network ACL rules to restrict traffic to only authorized sources and destinations.
  3. Implement network segmentation to isolate sensitive resources and limit access to them from other parts of the network.
  4. Consider using VPC peering or VPN connections to establish secure communication between different subnets or VPCs.
  5. Implement least privilege access controls for security groups and network ACLs, allowing only the minimum required access to resources.
  6. Regularly review and audit network configurations to ensure that they remain secure and compliant with organizational policies and best practices.

By implementing these measures, you can reduce the risk of unauthorized access and data exfiltration through cross transit connectivity in EC2 instances.

Enforced Resources
Note: Remediation steps provided by Lightlytics are meant to be suggestions and guidelines only. It is crucial to thoroughly verify and test any remediation steps before applying them to production environments. Each organization's infrastructure and security needs may differ, and blindly applying suggested remediation steps without proper testing could potentially cause unforeseen issues or vulnerabilities. Therefore, it is strongly recommended that you validate and customize any remediation steps to meet your organization's specific requirements and ensure that they align with your security policies and best practices.