In 1992, former hacker Jeff Moss invited a bunch of hacker friends he'd met primarily on electronic bulletin boards to come to Las Vegas to party in the desert. That party grew into a legendary conference that's become one of the premiere gatherings for hackers from around the world - as well as for undercover intelligence agents who want to spy on them (or recruit them).

More than 7,000 hackers and security professionals attend annually. Other hacker conferences have tried to copy DefCon's secret sauce throughout the years, but none have been able to match its successful mix of smart talks, organized chaos and hearty parties. Next month, DefCon will celebrate its 20th year, by bringing back some of the original speakers that made year one so special.