Lenny DiCicco
Kevin Mitnick's closest hacking partner in the 1980s, and eventually the man who handed him to the FBI.
In 1987–88 Leonard DiCicco and Mitnick broke into Digital Equipment's network and copied source code for the VMS operating system, partly using machines at DiCicco's workplace. It was the kind of friendship in which each side suspected the other, and by his own account Mitnick spent a fair amount of effort harassing DiCicco by phone.
In December 1988 DiCicco went to DEC's security staff and the FBI, then lured Mitnick to a parking lot where agents were waiting. Mitnick was sentenced in 1989 to a year in prison plus treatment for "computer addiction", a diagnosis that says more about the courts of the day than about Mitnick. The story is retold both in Jonathan Littman's book and in Mitnick's own.