You’ve set up a Classic Load Balancer and EC2 Instances behind the Load Balancer. The following Security Groups have been set.
· Security Group for the ELB – Accept Incoming traffic on port 80 from 0.0.0.0/0
· Security Group for the EC2 Instances – Accept Incoming traffic on port 80 from 0.0.0.0/0
It has been noticed that the EC2 Instances are getting a large number of direct requests from the Internet. What should be done to resolve the issue?
 

Answer options:

A.Change the ELB security group to only accept traffic from the EC2 Instances on port 80
B.Change the EC2 Instance security group to only accept traffic from the ELB Security Group on port 80
C.Change the ELB security group to only accept traffic from the EC2 Instances on port443
D.Change the EC2 Instance security group to only accept traffic from the ELB Security Group on port 443

Answer – B
The AWS Documentation mentions the following for how the security groups should be defined for the underlying EC2 Instances.
Option A is incorrect since the ELB needs to accept traffic from everywhere.
Options C and D are incorrect since there is no mention in the question of HTTPS traffic.
For more information on the Security Groups for Classic Load Balancers, please refer to the below URL
https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-security-groups.html