Mirai was the botnet that became notorious in 2016 for attacking internet-connected cameras and routers.
Mirai scanned the internet for devices using factory-set or easily guessed usernames and passwords. It recruited vulnerable Internet of Things devices into a botnet and used them to launch distributed denial-of-service attacks.
In October 2016, a Mirai-related attack against DNS provider Dyn caused access problems for many major websites, including services hosted by companies such as Twitter, Netflix, and Amazon. The event demonstrated how inexpensive consumer devices could create substantial internet disruption.
The original Mirai source code was later released publicly, contributing to the appearance of related variants. The incident highlighted basic security practices that remain important: changing default credentials, applying firmware updates, disabling unnecessary services, and separating IoT devices from more sensitive networks.