Amazon EC2 Security Groups and Firewall

When you launch your EC2 instance, you will be asked to specify a Security Group. You can specify one or more groups. I have one group which I use for public access and one that I use to specify behavoir for my home office. You may want to create groups for different locations.

So what do these Security Groups do? Security Groups act as your firewall to the instance. You can specify what protocols are allowed from what IP address. For example, you can specify HTTP, port 80, to be available from all address. You can also limit a protocol to an IP address. For example, you could limit SSH, port 22, to just one address.  You would specify SSH and the IP address, w.x.y.z/32 to mask it just to that address.