Add short section on OpenVPN

README.md

@@ -1488,6 +1488,7 @@ VPCs, Network Security, and Security Groups
 	-	You expose a smaller surface area for attack compared to exposing separate (potentially authenticated) services over the public internet.
 		-	e.g. A bug in the YAML parser used by the Ruby on Rails admin site is much less serious when the admin site is only visible to the private network and accessed through VPN.
 	-	Another common pattern (especially as deployments get larger, security or regulatory requirements get more stringent, or team sizes increase) is to provide a [bastion host](https://www.pandastrike.com/posts/20141113-bastion-hosts) behind a VPN through which all SSH connections need to transit.
+	-	For a cheap VPN to access private AWS resources, consider using a point-to-site software VPN such as [OpenVPN](https://openvpn.net/). It can either be installed using the [official AMI](https://docs.openvpn.net/how-to-tutorialsguides/virtual-platforms/amazon-ec2-appliance-ami-quick-start-guide/), though you are limited to 2 concurrent users on the free license, or it can be installed using the openvpn package on linux. The linux package allows for unlimited concurrent users but the installation is less straightforward. This [OpenVPN installer script](https://github.com/Nyr/openvpn-install) can help you install it and add client keys easily.
 -	🔹Consider using other security groups as sources for security group rules instead of using CIDRs — that way, all hosts in the source security group and only hosts in that security group are allowed access. This is a much more dynamic and secure way of managing security group rules.
 -	**VPC Flow Logs** allow you to monitor the network traffic to, from, and within your VPC. Logs are stored in CloudWatch Logs groups, and can be used for security monitoring (with third party tools), performance evaluation, and forensic investigation.
 	-	See the [VPC Flow Logs User Guide](http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/flow-logs.html) for basic information.