In February - 5 Million Home Routers used in DNS Amplification Attack

According to the article:- 

24 million home routers have open DNS proxies which potentially expose ISPs to DNS-based DDoS attacks.

Using home routers helps mask the attack target making it harder for ISPs to trace the ultimate recipient of the waves of amplified traffic.

"Even if ISPs employ best practices to protect their networks, they can still become victims, thanks to the inherent vulnerability in open DNS proxies".



The link below has more information:-

http://betanews.com/2014/04/02/millions-of-home-routers-expose-isps-to-ddos-attacks/