DNS, or Domain Name Service, is the protocol that turns all those numbers in your IP address to something that is human readable.
... It is broken and there are exploits out there that can redirect you to "bad places".
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Monday, July 28, 2008 10:53 AM PDTObey Browser Certificate Warnings Due to DNS Flaw
A few days ago, I wrote about a fundamental flaw in the Domain Name Service (DNS) protocol that handles the lookup from human-readable names into machine-processed Internet Protocol (IP) addresses, advising all readers to determine their vulnerability and take action.
There's one more warning I should pass on, however. Because this flaw allows an attacker to poison the DNS for anyone whose system connects to an unpatched DNS server, an attacker can also bypass a protection built into encrypted Web sessions
Pay attention if your browser warns you about an "invalid certificate". You may be having your session hijacked.