Which term best describes malware that forms a network of compromised hosts under centralized control?

• A. Shadow file
• B. Ransomware
• C. Botnet Trojans
• D. Boot Sector Virus

Answer: (C)

A botnet is a network of compromised machines that an attacker controls from a central point. Malware that creates such a network is commonly known as botnet trojans. A Trojan infects a host and installs a bot agent that reaches out to a command-and-control server or infrastructure. From there, the attacker can issue coordinated instructions to all the infected machines, making it possible to conduct large-scale actions like distributed attacks, spam campaigns, or data theft with centralized leadership over the fleet. This centralized control is the hallmark that sets botnets apart from stand-alone malware.

Shadow file is simply a system file that stores password hashes in some operating systems, not a malicious network. Ransomware is malware that encrypts users’ data for ransom but doesn’t inherently describe a network of compromised hosts under centralized control. A boot sector virus targets the boot sector of a disk to run on startup and isn’t about managing a network of infected devices.