To revist this article, visit My Profile, then View saved stories. In November 2003, security researcher Barrett Lyon was finishing college at California State University, Sacramento, while working full time as a penetration tester—a hacker companies hire to find weaknesses in their own digital systems. At the beginning of each job, Lyon would do some basic reconnaissance of the customer's infrastructure: “case the joint,” as he puts it. He realized he was essentially refining and repeating a formula to map what the new target network looked like. “That formula ended up being an easy piece of software to write, so I just started having this software do all the work for me,” Lyon says.