Last week, Telefônica Brasil was victim of a large DNS attack that shut down all their DNS farms affecting millions of broadband users for 3 days.
Additional info can be found at the following locations (portuguese):
6 months ago I wrote a post called "Securing DNS Servers" describing how to implement some security layers to increase the DNS farm performance and overall security.
It's important for us, Security Professionals to show to companies (Telco, Gov or Enterprises) the risk involved with critical services (like DNS, but not only) and the value of implementing procedures like BCDR. Not forgetting the technologies and services needed to secure the infrastructures.
The DNS post is located here: