I'm watching this hack in a demo video recorded by Manfred as I stand next to him in a Las Vegas bar on Thursday. Manfred, who asked me not to reveal his real name, says he has been hacking several video games for 20 years, making a real-life living by using hacks like the one I just witnessed. His modus operandi has changed slightly from game to game, but, in essence, it consisted of tricking games into giving him items or currency he doesn't have a right to have. He would then sell those items and currency to other players (for real money) or wholesales them to online gray markets, such as the Internet Game Exchange , that then would sell those goods to individual players.

Manfred's character is standing still in the virtual world of the 2014 sci-fi online multiplayer game WildStar Online. Manfred, the real life person behind the character, is typing commands into a debugger. In a few seconds of what seems to be an extremely easy hack, Manfred's virtual currency skyrockets up to more than 18,000,000,000,000,000,000, or 18 quintillion.

At the current exchange rate, Manfred estimates he has $397 trillion worth of WildStar gold. This is obviously an outlandish number, but, essentially, his income was only limited by the real-life market for the in-game currency.

"The best hacks are the invisible ones because you change the rules without anyone knowing what's going on."

When I spoke to Manfred ahead of his talk at the Def Con hacking conference, he said he wanted to go in, give his demo, and go out "as a ghost," never to be seen or heard from again. He said he wanted to be "invisible," just like he's been for the past two decades. He said he's found more than 100 publicly unknown vulnerabilities in more than 20 online video games, making hacking and trading virtual goods into his full time job.

Unlike most video game hackers, Manfred didn't cheat to gain an advantage over his opponents. He hacked games because he made it his living.

"The best hacks are the invisible ones because you change the rules without anyone knowing what's going on," Manfred told me. "When hacking online games, the main goal is to be invisible. You don't want to disrupt the players, you don't want the game company to find out about your hacks. You don't even want them to know that what you're doing is possible."

Read more: The Mystery of the Creepiest Television Hack

On Saturday, Manfred came out of the shadows and told his story for the first time during his talk. Initially, his plan was to hack WildStar Online in front of the audience, abusing undisclosed vulnerabilities, or zero-days, without having his talk recorded. The conference organizers, however, told him that all talks have to be recorded, and so he didn't do the hack live—much to the audience's chagrin.