Which activity would be useful in defending against thi…

A benefits enrollment company is hosting a 3-tier web application running in a VPC on AWS which includes a
NAT (Network Address Translation) instance in the public Web tier. There is enough provisioned capacity for
the expected workload tor the new fiscal year benefit enrollment period plus some extra overhead Enrollment
proceeds nicely for two days and then the web tier becomes unresponsive, upon investigation using
CloudWatch and other monitoring tools it is discovered that there is an extremely large and unanticipated
amount of inbound traffic coming from a set of 15 specific IP addresses over port 80 from a country where the
benefits company has no customers. The web tier instances are so overloaded that benefit enrollment
administrators cannot even SSH into them. Which activity would be useful in defending against this attack?

A.
Create a custom route table associated with the web tier and block the attacking IP addresses from the
IGW (internet Gateway)

B.
Change the EIP (Elastic IP Address) of the NAT instance in the web tier subnet and update the Main Route
Table with the new EIP

C.
Create 15 Security Group rules to block the attacking IP addresses over port 80

D.
Create an inbound NACL (Network Access control list) associated with the web tier subnet with deny rules
to block the attacking IP addresses