Back in 2004, a computer worm called Sasser swept across the web, infecting an estimated quarter million PCs. One of them belonged to Daniel White, then 16 years old. In the course of figuring out how to purge the worm from his system, the teenager came across the website of anti-virus company F-Secure, which hosted a vast field guide of malware dating back to the 1980s, complete with explanations, technical write-ups, and even screenshots for scores of antiquated viruses. He found it intoxicating. “I just read all I could,” he says, “and when I’d read all of that I found more sources to read.” He’d caught the computer virus bug.