A group of Cisco CallManager servers needs to be secured from viruses that may propagate over the network. Which of these steps will provide the most security? (Choose two)

A.
Stop using Internet Explorer on Cisco CallManager servers.

B.
Apply operating system patches regularly and often.

C.
Close down all server ports except port 80.

D.
Shut down FTP services on all servers.

E.
Install approved antivirus software.

F.
Apply latest antivirus updates and virus definition files.