In order to coordinate the activity of many infected computers, attackers have used coordinating systems
known as:

A.
wormnets

B.
trojannets

C.
spynets

D.
botnets

E.
rootnets

F.
backdoor

Explanation:
In order to coordinate the activity of many infected computers, attackers ave used coordinating systems known
as botnets. In a botnet, the malware or malbot logs in to an Internet Relay Chat channel or other chat system.
The attacker can then give instructions to all the infected systems simultaneously.