How Does a Botnet Work?
A botnet is a collection of Internet-connected devices that have been infected with malware and are controlled remotely by a cybercriminal. The compromised systems (called “bots”), which can include computers, mobile phones, IoT gadgets, and routers, execute commands without the users’ knowledge or consent. These automated devices form the basis for many large-scale cyberattacks, including DDoS attacks, data theft, and spamming. Understanding how botnets work is essential for cybersecurity professionals defending against these threats.
A malicious bot is a piece of software that infects a device, steals data, and transmits that information to the malware’s creator—the “bot herder.” From there, the bot-herder can command the devices in the network to perform a variety of tasks, such as launching DDoS attacks, stealing login credentials, spamming victims, or spreading additional malware to other devices on the network.
Most botnets are created by malware injected through security vulnerabilities in outdated software, phishing sites, or unsecured IoT devices that don’t have strong password protection. Once the bots are infected, they communicate with the bot-herder using a Command and Control (C2) server—typically hidden on the Dark Web—to receive instructions and transmit data back to the herder for use in cyberattacks.
Modern bots often employ resilience features to survive disruption attempts, such as fast-flux techniques that quickly change IP addresses associated with the C2 servers, complicating blacklisting efforts. They also utilize hybrid architectures that combine centralized C2 servers with peer-to-peer (P2P) communication networks that allow the bots to relay commands to each other.