One could view BeEF as a C&C, but … BeEF is a tool designed to provide effective client-side attack vectors and to exploit any potential vulnerabilities in the web browser. Ideal for demonstrating and explaining these attack vectors. It is unique among the C&C frameworks because it does not try to tackle the more secure network interface aspects of a system. These C&C’s can. With enough time later, we can give BYOB or Merlin a whirl.
With a centralised command and control model, a malware “client” will phone home to a C2 server and check for instructions. The server-side infrastructure can include redirectors, load balancers, and defense measures to detect security researchers and law enforcement. Public cloud services and Content Delivery Networks (CDNs) are often used to host or mask activity.
The domains and servers can be removed within hours of their first use, and the malware is often coded with a list of different C2 servers to try and reach.
In a P2P C2 model, command and control instructions are delivered to members of a botnet relaying messages between one another. Some nodes can function as server, but there is no central or master node. This makes it harder to detect or disrupt than a centralised model but can also make it more difficult to issue instructions to the entire botnet.
P2P networks can be used as a fallback mechanism in case the primary centralised C2 channel is disrupted.
Out of Band
Twitter, Gmail, IRC chat rooms, and even Pinterest can be used to issue C&C messages to compromised hosts.
Command and control infrastructure can even be random, and use scanning the Internet to find an infected host. This is extremely hard to take down.