Donn Parker
The SRI researcher who was cataloguing computer crime before most people believed there was such a thing.
Donn B. Parker joined SRI International in the late 1960s and spent decades building a file of real computer crimes – embezzlement, sabotage, fraud – while the rest of the industry was still debating hypothetical threats. His book Crime by Computer (1976) was one of the first systematic treatments of the subject, and he made a habit of interviewing the perpetrators directly.
He is most often cited for the Parkerian hexad (1998), which extends the familiar confidentiality–integrity–availability triad with possession, authenticity and utility. The point: a stolen but encrypted backup is still a security incident even if no secret leaks, and data encrypted under a lost key is perfectly intact and perfectly useless.