Q:

AWS Security Groups - EC2 to RDS

I wanted to ask about connecting EC2 to RDP in AWS.
I have added my EC2 Security Group (that contains the EC2 instances) into the Default RDP Group and Data is flowing - the connection works.
The EC2 Security group has Port 80 to 0.0.0.0/0 and SSH to my IP enabled.
I'm a touch concerned that by adding this EC2 group to the RDS Database it will allow Port 80 traffic from anywhere to access the Databases. Is this correct or wrong?
Do the rules in the EC2 apply to the RDS instances if you connect them like this?
I did read on the AWS websites that 'Database Security Groups only allow access to the database server port'. Can anyone confirm this is correct?
thankyou

A:

You do not need to worry about additional ports being opened up on RDS server.
The EC2 security groups are just treated like an access control list when used in RDS DB security policies.
Basically what you are saying is that you want to let any instances which belong to specific EC2 security group have access to the RDS instances using that DB security groups policy.
The specific rules defined in the EC2 security groups do not matter.
This behavior basically just gives you a convenient way to easily allow access from a cluster of servers with some common association (their security group).

