VPCs achieve high levels of security by creating virtualized replicas of the security features that control access to the resources that are housed in traditional data centers. You can define virtual networks in logically isolated parts of the public cloud. You can control which IP addresses have access to which resources.
Access control lists (ACLs) are lists of rules that limit who can access a particular subnet in your VPC. The ACL defines the set of IP addresses or applications that are granted access to the subnet.
You can create groups of resources, which may be situated in more than one subnet, and can assign uniform-access rules to them. Security groups act like virtual firewalls, controlling the flow of traffic to your virtual servers, no matter which subnet they reside in. \r