You are conducting a port scan on a subnet that has ICMP blocked. You have discovered 23 live systems and after scanning each of them you notice that they all show port 21 in closed state.

What should be the next logical step that should be performed?

A.
Connect to open ports to discover applications.

B.
Perform a ping sweep to identify any additional systems that might be up.

C.
Perform a SYN scan on port 21 to identify any additional systems that might be up.

D.
Rescan every computer to verify the results.

Explanation:
As ICMP is blocked you’ll have trouble determining which computers are up and running by using a ping sweep. As all the 23 computers that you had discovered earlier had port 21 closed, probably any additional, previously unknown, systems will also have port 21 closed. By running a SYN scan on port 21 over the target network you might get replies from additional systems.