Xie is a classic Silicon Valley success story whose business, cybersecurity, is hotter than ever. The stock of Fortinet, the company he and his brother Michael founded in 2000, has returned 190% over the past three years. Ken Xie, 57, started his first cybersecurity company as a Stanford graduate student, then in 1996 started another, which was sold to Juniper Networks. Fortinet, his third company, claims customers include Alibaba, Autodesk, Siemens, Volkswagen, and 70% of the Fortune 100. After 20 years in a crowded industry, it’s still growing revenue 19% a year with no long-term debt.