To improve ECS instance security, the administrator does not want users on public network to check whether an ECS instance is online using the ping command. Which of the following reinforcement measures designed by the administrator is NOT feasible?
A.
Resolve the IP address of the ECS instance to an uncommon level 4 domain name, and point the promotional domain name to the level 4 domain name through CNAME
B.
Enable a security group and only allow access from ports 80 and 25 of the public network through TCP
C.
Enable a security group, and reject ICMP for public network access.
D.
Enable an operating system firewall for the ECS instance, and reject ICMP for public network access.
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