"If you don't think the recent discovery of the DNS
cache-poisoning flaw is bad news and needs to be addressed as soon
as possible, let me repeat what Paul Mockapetris, DNS' (Domain Name
System) inventor, had to say about this security hole: Patch your
DNS servers right now.
"CERT can tell you about the technical details of DNS
cache-poisoning, here's what an attack on a DNS server can mean to
you according to Dan Kaminsky, a researcher at security services
firm IOActive: The vulnerability could allow attackers to redirect
Web traffic and e-mails to systems under their control..."