Fault injection techniques based on the use of VHDL as design language offer important advantages with regard to other fault injection techniques. First, as they can be applied during the design phase of the system, they allow reducing the time-to-market. Second, this type of techniques presents high controllability and reachability. Among the different techniques, those based on the use of saboteurs and mutants are especially attractive due to their high capability of fault modeling. However, it is difficult to implement automatically these techniques in a fault injection tool, mainly the insertion of saboteurs and the generation of mutants. In this paper, we present new models of saboteurs and mutants that can be easily applicable in VFIT, a fault injection tool developed by the Fault-Tolerant Systems Research Group (GSTF) of the Technical University of Valencia.