The botnet reuses some Mirai source code, but it's unique in its own right. Unlike Mirai, which relied on scanning for devices with weak or default passwords, this botnet was put together using exploits for unpatched vulnerabilities. The botnet's author is still struggling to control his botnet, as researchers spotted over two million infected devices sitting in the botnet's C&C servers' queue, waiting to be processed. As of now, the botnet has not been used in live DDoS attacks, but the capability is in there.
Today is the one-year anniversary of the Dyn DDoS attack, the article points out, adding that "This week both the FBI and Europol warned about the dangers of leaving Internet of Things devices exposed online."