In what kind of attack can attackers make use of hundreds of thousands of computers under their control in an attack against a single server or network?

DDoS

Explanation:

A distributed denial-of-service (DDoS) attack is a malicious attempt to disrupt the normal traffic of a targeted server, service or network by overwhelming the target or its surrounding infrastructure with a flood of Internet traffic.

DDoS attacks achieve effectiveness by utilizing multiple compromised computer systems as sources of attack traffic.

you have to first get good enough where you are an ace or master, then some of the creators could make you a mod. (this is pretty hard to do though)