Maybe the painkillers loosened something in his mind, because as Kaminsky began to think more deeply about DNS he became convinced that something wasn't right. He couldn't quite figure it out, but the feeling stuck with him even after he stopped taking the pain pills. He returned to work full time and bought a recumbent stationary bike. He got hired to test the security of Windows Vista before it was released, repeatedly punching holes in it for Microsoft. Still, in the back of his mind, he was sure that the entire DNS system was vulnerable to attack.

Then last January, on a drizzly Sunday afternoon, he flopped down on his bed, flipped open his laptop, and started playing games with DNS. He used a software program called Scapy to fire random queries at the system. He liked to see how it would respond and decided to ask for the location of a series of nonexistent Web pages at a Fortune 500 company. Then he tried to trick his DNS server in San Diego into thinking that he knew the location of the bogus pages.

Suddenly it worked. The server accepted one of the fake pages as real. But so what? He could now supply fake information for a page nobody would ever visit. Then he realized that the server was willing to accept more information from him. Since he had supplied data about one of the company's Web pages, it believed that he was an authoritative source for general information about the company's domain. The server didn't know that the Web page didn't exist—it was listening to Kaminsky now, as if it had been hypnotized.