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Security Group

  • A security group is a virtual firewall which is controlling the traffic to your EC2 instances.
  • When you first launch an EC2 instance, you can associate it with one or more security groups.
  • A Security group is the first defence against hackers.

Let's understand the concept of security group through an example.

  • Sign in to the AWS Management console.
  • Launch a new EC2 instance.
  • Choose an Amazon Machine Image.
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  • Choose the instance type. Suppose I choose the instance, i.e., t2.micro, and then click on the Next.
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  • Now, configure the Instance details. Keep all the details as default, and then click on the Next.
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  • Attach the EBS Volume to your EC2 instance. By default, Root is the default EBS volume which is attached to your EC2 instance. Click on the Next.
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  • Add tags.
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  • Configure Security Group. Select an existing security group that you created previously, i.e., WebServer.
Security Group
Security Group

The above screen shows that a WebServer is a security group that consists of inbound rules such as protocol, port range, and source address.

  • Click on the Review and Launch button.
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From the above screen, we observe that the security group, WebServer is open to the world means that SSH port is open to the world.

  • Click on the Launch button.
  • Create a new key-pair. A key-pair allows you to connect to your instance securely.
Security Group
  • Click on the Launch Instances.
  • A key-pair is generated with .pem extension. Convert the pem file into ppk file by using putygen tool.
  • Open the putty.
  • Enter the host name, i.e., ec2-user@18.222.2.1, and save the host name in a session logging.
  • Click on the SSH appearing on the right-side of the putty, move to the Auth and then attach the ppk file.
  • Run the command sudo su to move to the root level and then update the EC2 instance by running the command yum update -y.
  • Install the Apache server so that EC2 instance becomes a web server by running the command yum install httpd -y.
  • Run the command cd /var/www/html to set the path.
  • Now, create a text editor by using the command nano index.html.
  • Start the Apache server by running the command service httpd start.
  • After starting the server, copy the public IP address, and paste it to the browser.
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  • Security group consists of inbound rules, and the inbound rules are created by us only. Suppose I add three inbound rules, i.e., HTTP, SSH, and HTTPS.
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  • We can also delete the inbound rule. Suppose I want to delete the Http protocol, then click on the Edit button, and then click on the save button.
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Deleting the HTTP protocol from the security group would not allow us to see the Http, and this change is applied to the group immediately.

Note: An inbound rule consists of a source of the traffic and port range. If we are implementing any rules in the security group, then it happens very quickly.

  • We can also Edit the Outbound rule. Suppose I delete the All traffic rule, click on the Save button.
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Copy and paste an IP address to the web browser and run it.

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We got the same output. Therefore, we can say that it allows the traffic into an EC2 instance, and also will provide the responses without even any outbound rule set.

Note: When we add an inbound rule, then it automatically added in an outbound rule.

Move to the default security group. An Inbound rule of a default group consists of MYSQL/Aurora and RDP.

Security Group
  • We can add multiple groups to a single EC2 instance. Suppose I want to add a default security group to an EC2 instance. Move to the EC2 instance, click on the Actions dropdown menu. Move to the Networking, and then click on the Change Security Group.
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  • Now, check the default security group which you want to add to your EC2 instance.
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Some important points to remember:

  • All inbound traffic is blocked by Default, i.e., you need to add the traffic such as HTTP, HTTPs, etc.
  • All outbound traffic is allowed automatically.
  • You can have any number of EC2 instances within a security group.
  • You can have multiple security groups attached to EC2 instance./li>
  • Security groups are stateful, i.e., if you create an inbound rule allowing traffic in, that traffic is automatically allowed back out again.

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