The nick name for the four giant mainframe computers that are housed in the basement of Folcroft. Smith has personally built, modified and maintained these super-computers, even before there were super-computers. They execute Smith's complex software that filters out any and all information CURE needs, from every government agency, bank, the Internet, most corporations - basically if it can be reached by a network or phone-line, the Folcroft Four can get to the data - and get that data to Smith.
Even with the protocols, security, and trap-doors, the Folcroft Four do get broken into and used against Smith (and CURE) several times.
IDC does it. Friend does it. Other computer masterminds do it. Yet CURE still survives, thanks to our Destructive, Dynamic, Sinanju Duet - Remo and Chiun.