Which term describes networks of compromised computers controlled by an attacker?

• A. Botnet
• B. Worm
• C. Trojan
• D. Ransomware

Answer: (A)

A botnet is a network of compromised computers under an attacker’s remote control. Each infected device becomes a bot (or zombie) that can be commanded as part of a larger group, often through a central command-and-control server. This setup lets the attacker coordinate tasks at scale, such as launching distributed denial-of-service attacks, sending spam, or performing automated data theft. The key idea is collective control: many infected devices act together as directed by the attacker.

Worms self-propagate and spread without a centralized operator, Trojan horses conceal malicious functionality inside legitimate-looking software, and ransomware focuses on encrypting files and demanding payment rather than coordinating a network of compromised hosts.