Using security groups
Security groups control both inbound and outbound traffic, offering a robust line of defense against unauthorized access or unwanted traffic. In this section, we will delve into some of their most pertinent aspects for advanced AWS users and highlight some common pitfalls to steer clear of.
Significant aspects
Let’s explore some of the key functionalities that characterize security groups:
- Implicit deny rule: All security groups in AWS come with an implicit deny rule. This means that unless you explicitly allow a type of traffic, it will be automatically denied. This feature enforces the principle of least privilege, ensuring that only necessary traffic is allowed.
- Multiple security groups assignment: AWS allows you to assign multiple security groups to a single resource. This capability enables you to create and assign security groups based on specific categories, such as Linux, Windows, web servers, FTP servers, and so on. For instance, if you have an EC2 instance that functions as a Linux-based web server, you can assign it to both the Linux and Web Server security groups. This approach simplifies the management of your security groups and makes it easier to control access.
Trusting other security groups as a source: Security groups can trust other security groups instead of individual IP addresses. This feature is particularly useful in dynamic environments where IP addresses can change frequently. For example, you could have a security group named Web Server and another one named Database Server. Instead of allowing access from specific IP addresses, the Database Server security group’s rules can be configured to allow access from the Web Server security group. This ensures continuous access, even if the web server’s IP address varies. Furthermore, when using VPC peering, this method’s utility extends as you can reference security groups belonging to a peered VPC, adding an extra layer of flexibility. Managing access between VPCs becomes more straightforward, eliminating the need to track and update specific IP addresses. This method not only simplifies access management but also enhances security by ensuring that traffic between services is limited to authorized entities, independent of IP address changes.