AWS now makes it easier to manage your security groups with new security group sharing features. You can now associate a security group with multiple VPCs in the same account using Security Group VPC Associations. When using shared VPC, you can now also share security groups with participant accounts in that shared VPC using Shared Security Groups. This feature improves security group consistency and simplifies configuration and maintenance for your administrators.
Security Groups offer you control over the traffic that is allowed to reach and leave your VPC resources. You associate security groups to your VPC resources, such as EC2 instances, and define filtering rules to allow only trusted traffic for that resource. Prior to these features, a security group could be used only in the VPC for which it is created. With this feature, you can now use a security group with resources across VPCs and even across participant accounts in your shared VPC. This way, you can enforce consistent traffic filtering rules for workloads in your organization regardless of the VPC or the accounts.
Shared Security Groups and Security Groups VPC Associations is available in all commercial AWS Regions, the AWS GovCloud (US) Regions, and the China Regions.
To get started, see the following resources:
Shared Security Groups documentation
Security Groups VPC Association documentation
Source:: Amazon AWS