The name of a hacker group that existed from the late 80s through (at least) the middle to late 90s. They worked jointly on an e-zine with Phalcon called 40hex, a newsletter dedicated to the study, dissection, reconstruction and development of Computer Virus programs, and ultimately published Virus Constructor (also known as the VCL MPCG) which would auto-generate the code and binaries for polymorphic virus programs of all known forms (of the time.)
A term describing a collective of like-minded, notorious hackers, the term was more popular in the 80s and 90s and as the advent of the script kiddie took over in popularity the public focus on hacker groups (and thus, the use of the term) has waned. Examples of such hacker groups include l0pht, Phalcon/Skism and Legion of Doom.
Fact: "L0pht, a hacker group comprised of more than 50 members, announced at HOPE 2000 that they could take down the Internet within 30 minutes due to a fundamental flaw in the design and implementation of the TCP Internet Protocol."