An IT company hired you recently as Cloud Architect, and your Manager told you that the team is trying to host an Application on an EC2 Server with instance type as t2.micro. The team has created a security group named APP_SG and sent it for User Acceptance Testing where the tester complained that they cannot access the website. What could be the issue from the scenario?

Answer options:

A.Network ACL is blocking the user from accessing the application.
B.By default, the new security group allows no inbound traffic.
C.You should configure Network ACLs to allow all inbound traffic and allow all outbound traffic.
D.You should configure IAM Roles before using the application.

Correct Answer - B
Option A is incorrect because, by default, both inbound and outbound traffic is allowed.
Option B is CORRECT because the default rules for a custom security group that you create allows no inbound traffic and allows all outbound traffic.
There are two kinds of Security Groups:
Default Security Group
Custom Security Group
The following are the default rules for a Default Security Group:
- Allows all inbound traffic
- Allows all outbound traffic
In the question, a team has created a security group means it is a Custom Security Group. The below image signifies default rules for the custom security groups.
Option C is incorrect because Network ACLs are used for both allow and deny rules.
Option D is incorrect IAM Roles are used for Access management, not for traffic rules.
Reference:
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/default-custom-security-groups.html
https://docs.aws.amazon.com/vpc/latest/userguide/vpc-network-acls.html#nacl-rules