A botnet can be managed through which of the following?

IRC was the original and most widely used protocol for botnet C2 (command and control) because it allows a botmaster to broadcast commands to thousands of infected bots simultaneously through a shared channel. Infected machines connect to a designated IRC server and channel, continuously awaiting instructions from the operator. This pattern was established by early botnets such as SDBot and GTbot and remains a documented C2 technique.

While email-based C2 has appeared in some malware families, it is not the primary or traditional botnet management mechanism due to its asynchronous nature and susceptibility to filtering.

Social media platforms like LinkedIn and Facebook have been demonstrated in research as experimental C2 channels, but they are not the established or primary mechanism for operational botnets.

A vulnerable FTP server is a target for initial compromise or a staging area for malware delivery, not a protocol used to issue real-time commands to botnet members.