The computer virus population continues to grow, reaching the 300 mark. As the number and severity of virus incidents escalated, the need for reliable security rose proportionally. Early 1991 saw the appearance of more AV products: Norton AntiVirus from Peter Norton who now believed in viruses; Central Point Antivirus; Untouchable from Fifth Generation System. The latter were bought out by Symantec in 1993 and 1994.
Other virus writer bulletin boards modeled after the VX BBS and new personalities emerged from the computer underground: Cracker Jack (Italy – the Italian research Laboratory BBS), Gonorrhea (Germany); Demoralized Youth (Switzerland), Hellpit (USA) and Dead on Arrival and Semaj (UK). The computer underground was forming.
Tequila, a polymorphic boot infector, caused a significant epidemic in April of this year. It was created by a Swiss programmer exclusively for research purposes and without malicious intent. However, one copy of the virus was stolen by an acquaintance who consciously infected other users.
The summer of 1991 saw a virus epidemic with Dir_II using a fundamentally new means of infecting files: link-technology. This virus, to this day, remains the only example of this type detected in the wild.
Altogether, 1991 was relatively calm; a calm before the storm that broke in 1992.