It's July in Las Vegas, and the relentless midday desert sun has already pushed the outside temperature into three digits. But here inside the Alexis Park Resort, it's cool and dark. The bar is open, and the room is beginning to fill up. It's 1 p.m., the big game has just begun, and, as you'd expect in the world epicenter for sports gambling, the room glows with the light from dozens of screens catching every nuance of the action.But these aren't television screens, they're laptops. And the motley assortment of guys peering into them and busily clicking away at keyboards aren't gamblers looking to score some last-second intel on the game, they're hackersand this is the game.Welcome to Def Con, the self-proclaimed "largest underground hacking event in the world."