Security Groups Allowing Ingress from Broad Network Ranges


Security groups in AWS act as virtual firewalls, controlling inbound and outbound traffic to resources like EC2 instances. When a security group allows ingress from a broad IP range, such as /8, /16, or even /24, it increases the potential attack surface, as more IPs can interact with the associated resources. Such broad allowances might be necessary for specific scenarios, like a globally-distributed application, but they're often indicative of overly permissive configurations that need tightening for security purposes.


1. Identify Security Groups with Broad Ingress Rules:

AWS Management Console:
  • Navigate to the EC2 Dashboard.
  • In the left navigation pane, choose Security Groups.
  • Review the inbound rules for each security group, looking for rules that allow access from /8, /16, or /24 CIDR blocks.

2. Evaluate the Necessity of the Broad Rules:

For each security group with broad allowances:

  • Determine why the broad CIDR block was allowed. Consult with the resource or application owner if needed.
  • If the wide range is not needed, modify the rule to narrow down the IP range or remove it.
  • If a broader range is required, consider tightening the range or using VPC peering or a VPN for more secure access.
AWS Management Console:
  • For each identified security group, select the group and click on the Inbound rules tab.
  • Choose Edit inbound rules.
  • Modify or remove overly broad rules and save changes.

3. Implement Best Practices:

  • Always start with the least permissive rules and gradually add only the necessary permissions.
  • Regularly audit security groups for any overly permissive rules and update them.
  • Educate and train your team on the significance and best practices of AWS security groups.

4. Use Rapticore:

Rapticore can monitor and alert you when security groups with broad ingress rules are detected. Set up an appropriate alert.


Restricting inbound access to only necessary IP ranges based on the principle of least privilege can significantly reduce potential exposure to threats. While there might be use cases that require broader access, they should be exceptions and treated with added scrutiny. Regular audits, combined with tools like AWS Config, can help maintain a secure and compliant environment. When broad access is necessary, consider additional security layers, like application-level authentication, logging, monitoring, and anomaly detection, to offset the increased risk.