Vesselin Bontchev
Bulgarian virus researcher who documented the Bulgarian "virus factory" around 1990 and then spent decades taking malicious code apart.
In the late 1980s Bulgaria was an unlikely superpower in computer viruses: plenty of trained programmers, plenty of pirated PC clones and not much else to do. Bontchev, then at the Bulgarian Academy of Sciences, was among the first to describe the phenomenon systematically, notably in his 1991 paper on the "Bulgarian and Soviet virus factories". His favourite subject was Dark Avenger, whose polymorphic Mutation Engine made signature-based antivirus a considerably harder game.
He moved on to the Virus Test Center at the University of Hamburg and later to FRISK Software in Iceland, makers of F-Prot. There he stayed for many years as one of the industry's more pedantic voices on how malware should be classified and named.