Note that they want people with a good amount of experience and be ready to be grilled about technical concepts (explaining how they work/are exploited in detail). 3-4 interview stages starting with the CEO who is former NSA.

Thanks! We do focus on a technical interview, but not trivia. We really want to know where a candidate's expertise and passions lay. We try to do hands on as much as possible. Four stages would be unusual, typically the interview process includes a 30min phone screen followed by a technical panel. Sometimes there may also be a preliminary recruiting call to gauge interest.