A botnet is a network of infected computers, often called "bots" or "zombies," that are controlled by a cybercriminal. These bots are usually infected with malware, allowing the attacker to remotely control them without the owner's knowledge. Botnets can be used for various malicious activities, such as sending spam emails, stealing personal information, or launching attacks on websites. Cybercriminals often create botnets by exploiting vulnerabilities in software or tricking users into downloading harmful files. Once a computer is part of a botnet, it can be used alongside thousands of others to perform large-scale operations, making it difficult to trace back to the original attacker.