Located on the less fashionable north end of the Las Vegas strip, the Riviera Hotel and Casino has seen better days. Even the girls in posters for the hotel's topless revue could use a makeover. But hey, it's cheap. Which is why 6,000 hackers have descended upon it for DefCon, billed as the "largest underground hacking event in the world." So while the hotel is no doubt happy for the business, it's also