Krebs: IoT malware knocks out nearly a milllion Deutsche Telekom routers
According to BadCyber.com, which first blogged about the emergence of the new Mirai variant, part of the problem is that Deutsche Telekom does not appear to have followed the best practice of blocking the rest of the world from remotely managing these devices as well.
https://krebsonsecurity.com/2016/11/new-mirai-worm-knocks-900k-germans-offline/