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 Valkoinen Mökki Airport, Veltro's operation base, immediately attacking 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 Farfarello were encountered 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. that could be controlled while being administered proscribed sedatives. It also stated that these B.O.W.s were unpredictable and impossible to control without hourly sedation. During the transporting of the Farfarello's, their sedatives had worn off, explaining their attack on Il Veltro's base and aircraft.
Following Quint Cetcham's datamine of a II Veltro computer terminal and discovering incriminating evidence against Morgan Lansdale of the FBC, Morgan Lansdale ordered an airstrike bombing of the base. The airstrike bombing destroyed the entire facility and any B.O.W.s present.