Botnets act as a force multiplier for individual attackers, cyber-criminal groups and nation-states looking to disrupt or break into their targets’ systems. By definition, they are a collection of any type of internet-connected device that an attacker has compromised. Commonly used in distributed denial of service (DDoS) attacks, botnets can also send large volumes of spam, steal credentials at scale, or spy on people and organizations.
Malicious actors build botnets by infecting connected devices with malware and then managing them using a command and control server. Once an attacker has compromised a device on a specific network, all the vulnerable devices on that network are at risk of being infected.
Read more about botnets and why they are a persistent threat, on CSO.