Half of domain-name servers are open to attack
Half of the web’s domain name servers are wrongly configured, leaving companies and large sections of the internet infrastructure open to attack. The survey found that 50% of DNS servers allow recursive name services – a form of name resolution that often requires a name server to relay requests to other name servers.
http://www.computerweekly.com/Articles/2006/10/11/219071/Half+of+domain-name+servers+are+open+to+attack.htm