What is a Botnet?
A botnet is a network of computers or Internet of Things devices (IoT) that have been infected with malware and are controlled remotely by a hacker (also known as a bot herder). A bot can be used to perform various types of malicious activities, such as sending spam messages, participating in DDoS attacks, and stealing online credentials.
Cybercriminals create and operate botnets for a variety of reasons. Some want to steal personal data, while others look to sabotage websites and services by flooding them with traffic. Often, the hacker that controls a botnet sells or rents access to its zombie computers to other criminals.
When a bot is infected with malware, it communicates with a control center—also known as a C&C server—through covert channels. The server then sends instructions to the bot, which spreads them to the other machines in the botnet. Historically, bots used IRC networks and domains for communication, but newer versions often use components of decentralized peer-to-peer filesharing programs to transmit instructions. This makes them less susceptible to disruption by a single point of failure.
Bots are commonly distributed through phishing emails, software vulnerabilities, and mobile apps. Symptoms of infection include a device that suddenly slows down or becomes scorching hot when not in use. Infected devices can also use system resources to complete tasks for the bot herder, such as cryptocurrency mining or DDoS attack participation. These tasks can strain a device’s processor and battery, which may explain why the device feels so hot when it isn’t being used.