Routers, computers, web cameras — they all connect to the internet. And they can be infected with malicious software that lets someone else take over. The device becomes a bot, essentially.

A group of these devices networked together then becomes a botnet. And these botnets can then be used for nefarious purposes, like distributed denial of service attacks, without the device owners even knowing about it.

Cybersecurity journalist Brian Krebs recently wrote about several large botnets including one called Kimwolf that compromised more than three million devices.