Farfarello were developed by the terrorist group Il Veltro by administering the t-Abyss virus to regular Hunters. At some point, a pack of Farfarello broke free of their confinement at Veltro's operation base, and immediately attacked the terrorists. This also resulted in the crashing of a cargo plane that Chris Redfield witnessed, due to one of the Farfarello being sucked into the engine while it was attacking it. Later on the game, the Farfarello were exterminated by BSAA officers dispatched to the area. A file found near the crash site implied that these Hunters were intended to be a prototype B.O.W., and that their sedatives had worn off, explaining their attack on Il Veltro.